diff --git a/learning/exercises/ex3_4_5.go b/learning/exercises/ex3_4_5.go
new file mode 100644
index 0000000..bbf345a
--- /dev/null
+++ b/learning/exercises/ex3_4_5.go
@@ -0,0 +1,27 @@
+package exercises
+
+import (
+	"fmt"
+
+	"github.com/plasmus777/go_lang/learning/exercises/model"
+)
+
+// Create a model for item purchases containing: the date of ocurrence, the market's name and the bought items list.
+// Have the model on a specific "model" package and create a function to initialize a model and return its related struct using pointers.
+func Ex3_4_5() {
+	// purchase, error := model.InitializePurchase("")
+	purchase, error := model.InitializePurchase("Basic Market")
+	if error != nil {
+		fmt.Println("Error:", error)
+	} else {
+		purchase.AddItem2("Apple (1 pound)", 3, 1.29)
+		purchase.AddItem2("Pear (1 pound)", 2, 1.34)
+		purchase.AddItem2("Car Battery Charger", 1, 20.59)
+		purchase.AddItem2("Indoor Fly Trap", 1, 14.91)
+
+		fmt.Println("Market:", purchase.Market)
+		fmt.Println("Time of the purchase:", purchase.PurchaseTime)
+		fmt.Println("-------- Bought Items --------")
+		purchase.ListItems()
+	}
+}
diff --git a/learning/exercises/model/purchase.go b/learning/exercises/model/purchase.go
new file mode 100644
index 0000000..3b2f64f
--- /dev/null
+++ b/learning/exercises/model/purchase.go
@@ -0,0 +1,56 @@
+package model
+
+import (
+	"errors"
+	"fmt"
+	"time"
+)
+
+type Purchase struct {
+	Market       string
+	PurchaseTime time.Time
+	Items        map[string]Item
+}
+
+func InitializePurchase(name string) (*Purchase, error) {
+	if len(name) == 0 {
+		return nil, errors.New("The market's name cannot be empty.")
+	}
+
+	purchase := Purchase{
+		Market:       name,
+		PurchaseTime: time.Now(),
+		Items:        make(map[string]Item),
+	}
+
+	return &purchase, nil
+}
+
+func (p *Purchase) AddItem1(i Item) {
+	p.Items[i.Name] = i
+}
+
+func (p *Purchase) AddItem2(name string, number int, price float64) {
+	p.Items[name] = Item{
+		Name:   name,
+		Number: number,
+		Price:  price,
+	}
+}
+
+func (p *Purchase) GetTotalValue() float64 {
+	var totalValue float64
+
+	for _, item := range p.Items {
+		totalValue += item.GetTotalValue()
+	}
+
+	return totalValue
+}
+
+func (p *Purchase) ListItems() {
+	for _, item := range p.Items {
+		item.PrintItem()
+	}
+	fmt.Println("\nTotal: $", p.GetTotalValue())
+}
diff --git a/learning/exercises/model/purchase_item.go b/learning/exercises/model/purchase_item.go
new file mode 100644
index 0000000..cce7970
--- /dev/null
+++ b/learning/exercises/model/purchase_item.go
@@ -0,0 +1,19 @@
+package model
+
+import "fmt"
+
+type Item struct {
+	Name   string
+	Number int
+	Price  float64
+}
+
+func (i *Item) GetTotalValue() float64 {
+	totalValue := float64(i.Number) * i.Price
+
+	return totalValue
+}
+
+func (i *Item) PrintItem() {
+	fmt.Println(i.Number, "X", i.Name, " - $", i.GetTotalValue(), " ($", i.Price, " each)")
+}
diff --git a/learning/interfaces/interfaces.go b/learning/interfaces/interfaces.go
new file mode 100644
index 0000000..0ecf0b6
--- /dev/null
+++ b/learning/interfaces/interfaces.go
@@ -0,0 +1,5 @@
+package interfaces
+
+func Interfaces() {
+
+}
diff --git a/learning/main.go b/learning/main.go
index df9810c..c1c6654 100644
--- a/learning/main.go
+++ b/learning/main.go
@@ -6,12 +6,13 @@ import (
 	"github.com/plasmus777/go_lang/learning/arrays"
 	"github.com/plasmus777/go_lang/learning/fluxcontrol"
 	"github.com/plasmus777/go_lang/learning/inheritance"
+	"github.com/plasmus777/go_lang/learning/interfaces"
 	"github.com/plasmus777/go_lang/learning/simple"
 )
 
 func main() {
 
-	//exercises.Ex2()
+	// exercises.Ex3_4_5()
 
 	input := 1
 
@@ -34,6 +35,7 @@ func main() {
 		fmt.Println("13 - pointers")
 		fmt.Println("14 - structs")
 		fmt.Println("15 - inheritance")
+		fmt.Println("16 - interfaces")
 
 		fmt.Println("")
 		fmt.Println("-1 - exit")
@@ -87,6 +89,9 @@ func main() {
 		case 15:
 			inheritance.Inheritance()
 
+		case 16:
+			interfaces.Interfaces()
+
 		case -1:
 			fmt.Println("Exiting program.")
 			return