Add calc-account-ret-fee package with Solana dependencies

code/account/calc-account-ret-fee/Cargo.toml

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+[package]
+name = "calc-account-ret-fee"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+solana-client = "1.16.6"
+solana-sdk = "1.16.6"

code/account/calc-account-ret-fee/src/main.rs

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+// 计算账户费用
+// 在Solana上保持账户活跃会产生一项存储费用，称为 租金/rent。
+// 通过存入至少两年租金的金额，你可以使账户完全免除租金收取。
+// 对于费用的计算，你需要考虑你打算在账户中存储的数据量。
+use solana_client::rpc_client::RpcClient;
+use solana_sdk::commitment_config::CommitmentConfig;
+
+fn main() {
+    let rpc_url = String::from("http://127.0.0.1:8899");
+    let connection = RpcClient::new_with_commitment(rpc_url, CommitmentConfig::confirmed());
+    let data_length = 1500;
+
+    let rent_exemption_amount = connection
+        .get_minimum_balance_for_rent_exemption(data_length)
+        .unwrap();
+
+    println!("rent exemption amount: {}", rent_exemption_amount);
+}