Your friend promises you a perpetuity of $1 every year. The first payment occurs in year 1 , the interest rate is 10%, and there are no payments in years 8 and 10 , because your friend will be short of money in these two years. Except for years 8 and 10, the payment is always $1 in other years. Which of the following is right about its present value at time zero? a. $8.12 b. $9.15 c. $10.24 d. $11.31 e. None of the above