Exercise : BankAccount transfer

• Write an instance method transfer that moves money from this bank account to another account. The method takes two parameters: a BankAccount to accept money, and a real number for the amount to transfer. There is a $5.00 fee for transferring, to be deducted from the current account's balance.
• The method should modify the two objects such that "this" has its balance decreased by the given amount plus $5 fee, and the other's balance is increased by the given amount. A transfer also counts as a transaction on both accounts. If this account object does not have enough money to make the full transfer, transfer whatever money is left after the $5 fee is deducted. If this account has under $5 or the amount is 0 or less, no transfer should occur and neither account's state should be modified.
• For example, the following calls would produce the following results:

  BankAccount ben = new BankAccount("Benson", 90.00);
  BankAccount mar = new BankAccount("Marty",  25.00);
  ben.transfer(mar, 20.00);     // ben $65, mar $45   (ben loses $25, mar gains $20)
  ben.transfer(mar, 10.00);     // ben $50, mar $55   (ben loses $15, mar gains $10)
  ben.transfer(mar, -1);        // ben $50, mar $55   (no effect; negative amount)
  mar.transfer(ben, 39.00);     // ben $89, mar $11   (mar loses $44, ben gains $39)
  mar.transfer(ben, 50.00);     // ben $95, mar $ 0   (mar loses $11, ben gains $ 6)
  mar.transfer(ben,  1.00);     // ben $95, mar $ 0   (no effect; no money in account)
  ben.transfer(mar, 88.00);     // ben $ 2, mar $88   (ben loses $93, mar gains $88)
  ben.transfer(mar,  1.00);     // ben $ 2, mar $88   (no effect; can't afford fee)