public void PayIn(decimal amount) => _balance += amount;
static void Main() { IBankAccount venusAccount = new SaverAccount(); IBankAccount jupiterAccount = new GoldAccount(); venusAccount.PayIn(200); venusAccount.Withdraw(100); WriteLine(venusAccount.ToString()); jupiterAccount.PayIn(500); jupiterAccount.Withdraw(600); jupiterAccount.Withdraw(100); WriteLine(jupiterAccount.ToString()); }