investmentCalc() -- The simple interest formula, compounded yearly, is given by the formula: 

      A = P(1 + r)





where A = The total amount of money you have after the investment
      P = Principle, the amount of money you invested
      r = rate, the interest rate of the investment
      n = number of years the investment grows.  

Write a method that returns A (the amount) to the nearest dollar, given P, r, and n as parameters.