A $1,000 par bond with 22 years to maturity and a 4% semiannual coupon has a yield to maturity of 5%. Assuming a 5 basis point change in yield, what’s the convexity of this bond？
　　A.258
　　B.502
　　C.942
　　D.129
　　Answer: A
　　N = 2×22; PMT = 40/2; FV = 1,000; I/Y = 5/2; CPT→PV = 867.481 = V0
　　N = 2×22; PMT = 40/2; FV = 1,000; I/Y = 5.05/2; CPT→PV = 861.484 = V+
　　N = 2×22; PMT = 40/2; FV = 1,000; I/Y = 4.95/2; CPT→PV = 873.534 = V-