Find the present value of an annuity that pays $6000 at the end of each 6-month period for 8 years if the interest rate is 8% compounded semiannually.

According to my book, the answer is $69,913.77

I don't understand why?

according to my method i get another answer..

An = 6000 [ 1- (1+0.01)^-16/.01 = 90,000

what am i doing wrong?

thanks.