Assume that you wish to purchase a 20-year bond that has a maturity value of $1,000 and makes semiannual interest payments of $40. If you require a 10 percent effective annual return on your investment, what is the maximum price you should be willing to pay for the bond? (pick the closest number)

a. $674

b. $761

c. $828

d. $846

e. 902

The answer is d. 846$, but I cannot seem to come to that in my calculations. Please show all your work thanks :)