Your friend promises you a perpetuity of $1 every year, which starts in year 1. However, your friend is an absent-minded guy, paying you $2 at year 12 but no payment at year 8. Except for these two years, in other years, the payment is always $1. Which of the following is right about the present value at year zero of your friend's all payments if r = 5%? Select one: a. $21.03 b. $19.66 c. $20.03 d. $20.34 e. None of the above