diff --git a/src/main/java/me/alex4386/gachon/sw14462/day06/CheckService.java b/src/main/java/me/alex4386/gachon/sw14462/day06/CheckService.java
new file mode 100644
index 0000000..a03c479
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day06/CheckService.java
@@ -0,0 +1,20 @@
+package me.alex4386.gachon.sw14462.day06;
+
+public class CheckService {
+    public static double acceptCheck(double checkAmount) {
+        double fee = 0;
+        if (checkAmount < 10) {
+            fee = 1;
+        } else if (checkAmount < 100) {
+            fee = 0.1 * checkAmount;
+        } else if (checkAmount < 1000) {
+            fee = 5;
+            fee += 0.05 * checkAmount;
+        } else {
+            fee = 40;
+            fee += 0.01 * checkAmount;
+        }
+
+        return fee;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day06/GradeConverter.java b/src/main/java/me/alex4386/gachon/sw14462/day06/GradeConverter.java
new file mode 100644
index 0000000..da43f36
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day06/GradeConverter.java
@@ -0,0 +1,27 @@
+package me.alex4386.gachon.sw14462.day06;
+
+public class GradeConverter {
+    public static double letterGradeToGradePoint(char grade) {
+        double point = 0.0;
+        switch (grade) {
+            case 'A':
+                point = 4.0;
+                break;
+            case 'B':
+                point = 3.0;
+                break;
+            case 'C':
+                point = 2.0;
+                break;
+            case 'D':
+                point = 1.0;
+                break;
+            case 'F':
+            default:
+                point = 0.0;
+                break;
+        }
+
+        return point;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day06/GradeStatistics.java b/src/main/java/me/alex4386/gachon/sw14462/day06/GradeStatistics.java
new file mode 100644
index 0000000..04104be
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day06/GradeStatistics.java
@@ -0,0 +1,65 @@
+package me.alex4386.gachon.sw14462.day06;
+
+public class GradeStatistics extends IntegerStatistics {
+
+    int aCount = 0;
+    int bCount = 0;
+    int cCount = 0;
+    int dCount = 0;
+    int fCount = 0;
+
+    public GradeStatistics() {
+        total = 0;
+        count = 0;
+    }
+
+    @Override
+    public boolean add(int value) throws IllegalArgumentException {
+        if (value > 100) {
+            throw new IllegalArgumentException("Grade must be between 0 and 100");
+        }
+
+        boolean isValid = super.add(value);
+        if (isValid) {
+            switch (value / 10) {
+                case 10:
+                case 9:
+                    aCount++;
+                    break;
+                case 8:
+                    bCount++;
+                    break;
+                case 7:
+                    cCount++;
+                    break;
+                case 6:
+                    dCount++;
+                    break;
+                default:
+                    fCount++;
+                    break;
+            }
+        }
+        return false;
+    }
+
+    public int getACount() {
+        return aCount;
+    }
+
+    public int getBCount() {
+        return bCount;
+    }
+
+    public int getCCount() {
+        return cCount;
+    }
+
+    public int getDCount() {
+        return dCount;
+    }
+
+    public int getFCount() {
+        return fCount;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day06/IntegerStatistics.java b/src/main/java/me/alex4386/gachon/sw14462/day06/IntegerStatistics.java
new file mode 100644
index 0000000..a338139
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day06/IntegerStatistics.java
@@ -0,0 +1,53 @@
+package me.alex4386.gachon.sw14462.day06;
+
+public class IntegerStatistics {
+    long total;
+    int count;
+
+    int max = Integer.MIN_VALUE;
+    int min = Integer.MAX_VALUE;
+
+    boolean finalized = false;
+
+    public IntegerStatistics() {
+        total = 0;
+        count = 0;
+    }
+
+    public boolean add(int value) {
+        if (finalized) return true;
+
+        if (value < 0) {
+            this.finalized = true;
+            return true;
+        }
+
+        if (value < min) min = value;
+        if (value > max) max = value;
+
+        total += value;
+        count++;
+
+        return false;
+    }
+
+    public boolean hasFinalized() {
+        return this.finalized;
+    }
+
+    public int getMin() {
+        return this.min;
+    }
+
+    public int getMax() {
+        return this.max;
+    }
+
+    public int getCount() {
+        return this.count;
+    }
+
+    public double getAverage() {
+        return ((double) total) / count;
+    }
+}
diff --git a/src/main/java/me/alex4386/gachon/sw14462/day06/Main.java b/src/main/java/me/alex4386/gachon/sw14462/day06/Main.java
new file mode 100644
index 0000000..2637857
--- /dev/null
+++ b/src/main/java/me/alex4386/gachon/sw14462/day06/Main.java
@@ -0,0 +1,144 @@
+package me.alex4386.gachon.sw14462.day06;
+
+import me.alex4386.gachon.sw14462.day03.CoinPayment;
+import me.alex4386.gachon.sw14462.day03.coins.CoinImpl;
+import me.alex4386.gachon.sw14462.day05.Ex3_3;
+import me.alex4386.gachon.sw14462.day05.Ex3_6;
+import me.alex4386.gachon.sw14462.day05.Ex3_7;
+
+import java.util.List;
+import java.util.Scanner;
+
+public class Main {
+
+    static Scanner scanner = null;
+
+    public static Scanner getScanner() {
+        if (scanner == null) {
+            scanner = new Scanner(System.in);
+        }
+
+        return scanner;
+    }
+
+    public static void main(String[] args) {
+        System.out.println("Practice 3.1");
+        System.out.println("Practice 3.1a. Write a cashing program");
+        Main.exercise3_1a();
+        System.out.println("");
+
+        System.out.println("Practice 3.1b. Extend the existing get charge coins");
+        Main.exercise3_1b();
+        System.out.println("");
+
+        System.out.println("Practice 3.1c. Write a letter grade converter using switch statement");
+        Main.exercise3_1c();
+        System.out.println("");
+        System.out.println("");
+
+        System.out.println("Practice 3.2");
+        System.out.println("Practice 3.2a. Write an integer collection/statistics program");
+        Main.exercise3_2a();
+
+        System.out.println("Practice 3.2b. Extend collection/statistics program for grading");
+        Main.exercise3_2b();
+
+        System.out.println("");
+        System.out.println("");
+
+        System.out.println("Textbook Programming Project ----");
+        System.out.println("Exercise 3.3. Write a program that reads a bank account balance and an interest rate and displays the value of the account in ten years.");
+        System.out.println("ClassPath: "+ Ex3_3.class.getCanonicalName());
+        Ex3_3.main(args);
+        System.out.println("");
+
+        System.out.println("Exercise 3.6. Write a program that asks the user to enter the size of a triangle.");
+        System.out.println("ClassPath: "+ Ex3_6.class.getCanonicalName());
+        Ex3_6.main(args);
+        System.out.println("");
+
+        System.out.println("Exercise 3.7. Write a program that simulates a bouncing ball by computing its height in feet at each second as time passes on a simulated clock.");
+        System.out.println("ClassPath: "+ Ex3_7.class.getCanonicalName());
+        Ex3_7.main(args);
+        System.out.println("");
+    }
+
+    public static void exercise3_1a() {
+        System.out.print("Enter the amount of check: ");
+        double checkAmount = getScanner().nextDouble();
+
+        double charge = CheckService.acceptCheck(checkAmount);
+        System.out.println("The charge is $"+charge);
+    }
+
+    public static void exercise3_1b() {
+        System.out.print("Enter the price (in cents): ");
+        int price = getScanner().nextInt();
+
+        if (price < 25 || price % 5 != 0 || price > 100) {
+            System.err.println("Invalid input. Please enter a number between 25 and 100, divisible by 5.");
+        } else {
+            int payCharge = 100 - price;
+
+            try {
+                CoinPayment chargePayment = new CoinPayment(payCharge);
+                List<CoinImpl> paidCoins = chargePayment.pay();
+
+                System.out.println("Charge coins:");
+                for (CoinImpl coin : CoinPayment.coins) {
+                    int count = 0;
+                    for (CoinImpl paidCoin : paidCoins) {
+                        if (paidCoin.getClass().equals(coin.getClass())) {
+                            count++;
+                        }
+                    }
+                    System.out.println(coin.toString() + ": " + count);
+                }
+            } catch (IllegalArgumentException e) {
+                System.err.println(e.getMessage());
+            }
+        }
+    }
+
+    public static void exercise3_1c() {
+        System.out.print("Enter the letter based grade: ");
+        char character = getScanner().next().charAt(0);
+
+        double gradePoint = GradeConverter.letterGradeToGradePoint(character);
+        System.out.println("The letter grade is "+gradePoint+".");
+    }
+
+    public static void exercise3_2a() {
+        IntegerStatistics stats = new IntegerStatistics();
+
+        while (!stats.hasFinalized()) {
+            System.out.print("Enter the integer: ");
+            int integer = getScanner().nextInt();
+
+            stats.add(integer);
+        }
+
+        System.out.println("Max: "+stats.getMax());
+        System.out.println("Min: "+stats.getMin());
+        System.out.println("Avg: "+stats.getAverage());
+    }
+
+    public static void exercise3_2b() {
+        GradeStatistics stats = new GradeStatistics();
+
+        while (!stats.hasFinalized()) {
+            System.out.print("Enter the score: ");
+            int score = getScanner().nextInt();
+
+            stats.add(score);
+        }
+
+        System.out.println("total count: "+stats.getCount());
+        System.out.print("A count: "+stats.getACount()+" ");
+        System.out.print("B count: "+stats.getBCount()+" ");
+        System.out.print("C count: "+stats.getCCount()+" ");
+        System.out.print("D count: "+stats.getDCount()+" ");
+        System.out.print("F count: "+stats.getFCount()+"");
+        System.out.println("");
+    }
+}