Consider a perpetuity with a coupon rate of 5% pa. Coupons are paid annually. It is currently priced to yield 8% pa. Today is exactly nine months (three-quarters of a year) before the next coupon payment date. The current duration of this perpetuity is: (A) 12.75 years (B) 13.125 years (C) 13.25 years (D) 13.5 years