Charge a $5 penalty if an attempt is made to withdraw more money than available in the account. Here the account string is "S" or "C". "S" is for savings account. "C" is for checking account. For the deposit or withdraw, it indicates which account is affected. For a transfer it indicates the account from which the money is taken; the money is automatically transferred to the other account.

C++ code is explained below

Explanation:

class Account {

 double balance;

 double add(double sum) {

   balance += sum;

   return sum;  

 }

 double withdraw(double sum) {

   if (sum > balance) {  

     balance -= 5;

     return -5; // this will come in handy in Prob. 6  

   } else {  

     balance -= sum;

     return balance; // Notice: always >= 0 (never < 0)

   }

 }

 double inquire() { return balance; }  

 Account() { balance = 0; }

 Account(double sum) { balance = sum; }

 double interest (double rate) {

   return rate * balance;  

 }

}

class Bank {

 Account checking;

 Account savings;  

 void deposit(double amount, String account) {

   if (account.equals("C")) checking.add(amount);  

   else // my default

     savings.add(amount);  

 }

 void withdraw(double amount, String account) {

   if (account.equals("C")) checking.withdraw(amount);  

   else // my default

     savings.withdraw(amount);  

 }

 void transfer (double amount, String account) {

   if (account.equals("C"))  

     if (checking.withdraw(amount) >= 0)  

       savings.add(amount);  

     else checking.add(5); // somewhat fault-tolerant

   else // default

     if (savings.withdraw(amount) >= 0)  

       checking.add(amount);  

     else savings.add(5);  // no penalty for transfers

 }

 void printBalances() {

   System.out.println(

     "Checking: " + checking.inquire() +

     "\nSavings: " + savings.inquire()

   );  

 }

}