Ninety days ago, you purchased a 180-day Treasury bill with a face value of $500,000. At the time of your purchase, the yield to maturity on the bill was 6.0% p.a. If the current yield to maturity on the bill is 4.0% p.a. the price of the bill today is closest to: 

a) $485,631. 

b) $490,328. 

c) $492,711. 

d) $495,117.