Gretta wants to retire in 13 years. At that time she wants to be able to withdraw $12,500 at the end of each 6 months for 7 years. Assume that money can be deposited at 8% per year compounded semiannually. What exact amount will Gretta need in 13 years?

a) 138,979.88

b) 124,820.63

c) 132,039.00

d) 492,961.00