Write a class SavingsAccount that is similar to the BankAccount class, except that it has an added instance variable interest. Supply a constructor that sets both the initial balance and the interest rate. Supply a method addInterest (with no explicit parameter) that adds interest to the account. Write a SavingsAccountTester class that constructs a savings account with an initial balance of $1,000 and an interest rate of 10 percent. Then apply the addInterest method and print the resulting balance. Also compute the expected result by hand and print it.