A bond portfolio consists of a two-year zero-coupon bond with a face value of $4,000 and a 15-year zero-coupon bond with a face value of $8,000. The current yield on these bonds is 10% per annum (continuously compounded). Assume a 2% per annum increase in yields, please calculate the actual percentage change in the portfolio value and compare it with the estimated percentage changes in the portfolio value using two methods: (1) applying duration alone, (2) applying duration and convexity. Select one: O a. Actual change = -11.6896; estimated changes: (1) - -13.17%, (2) - -11.53% b. Actual change = -12.73%; estimated changes: (1) = -11.97%, (2) = -12.57% Oc. Actual change = -13-35%; estimated changes: (1) = -13.47%, (2) = -13.22% d. Actual change = -14.21%; estimated changes: (1) = -14.78%, (2) = -14.56%