88 a An employee invests 500 per month in an ordinary annuity If the interest rate is 5 find the value of the annuity after 18 yr b If the employee invests 1000 per month in the annuity instead of 500 at 5 interest find the value of the annuity after 18 yr Compare the result to part a e If the employee invests 500 per month in the annuity at 5 interest find the value of the annuity after 36 yr Compare the result to part a