31:39 (2X)
我是这样答的：
duration matching for multiple liabilities needs to be
1. market value of the asset exceeds or equal to the present value of the liability
2. BPV of asset equals to the BPV of the liability
3. asset convexity is larger than the liabilities convexity.
portfolio C is best because its BPV 11,005 is closely matched with the liabilities BPV 10,505 and the convexity 50.25 is bigger than the convexity of the liabilities' convexity 35.68.
第一个条件liability的PV还是MV？我看single liab写PV multiple写MV
