Which of the following statements are true? X: For a zero-coupon bond, the Macaulay duration is equal to the maturity. Y: For i > 0 the duration for a perpetuity is infinite. Z: As a coupon-paying bond pays coupons, the duration becomes longer after each payment. a) Only X is true b) Only Y is true c) Only Z is true d) Only X and Y are true e) Only X and Z are true f) Only Y and Z are true g) All of X, Y, and Z are true Oh) None of X, Y, or Z are true