这里的duration怎么匹配

NO.PZ2023032703000035 问题如下 Ams anjunior portfolio manager Frank Neeson review the fixeincome portfolios of two new finebenefit plclients, Lawson ors Cabinets, Inc., anWharton Farms. Lawson’s plh30 participants, who are mostly experiencecraftsmen anmachinists, whereWharton hover 100 participants in its plan. The average participant age is 15 years younger for the Wharton plcomparewith the Lawson plan. In both plans, participants receive a monthly benefit upon retirement baseon average finpanhave no option for a lump sum stribution. The two plans’ portfolio characteristiare shown in Exhibit 2.Ams states to Neeson, “For the Lawson anWharton plans, we cconsir one of three alternative strategies to manage the multiple liabilities associatewith these plans. Whenever a plan’s surplus is less th5%, we favor passive management strategies.”Whiof the following three strategies is least likely appropriate for the plans in Exhibit 2? (2019 moAM) A.ration matching B.Cash flow matching C.Contingent immunization B is correct. Cash flow matching is least appropriate for both plans. In both the Lawson anWharton plans, participants are entitleto receive a monthly benefit. Cash flow matching entails builng a cateportfolio of zero-coupon or fixeincome bon to ensure there are sufficient cash inflows to pthe schelecash outflows. However, sua strategy is impracticancleto large cash flow holngs between payment tes, resulting in reinvestment risk anforgone returns on cash holngs.C is incorrect. Contingent immunization is appropriate strategy for both plans. Contingent immunization allows for active bonportfolio management until a minimum thresholin the surplus is reache The thresholof 5% (of assets greater thliabilities) is exceein both plans; the Lawson portfolio ha surplus of 7.7%, anthe Wharton portfolio ha surplus of 11.8%.A is incorrect. ration management is also appropriate for both the Lawson anWharton plans. In this case, however, because they enjoy a surplus of assets to liabilities, the contingent immunization strategy is most appropriate. Sinthe plans are in the process of being aisePavoniWharton woullikely aiseto eliminate the ration gin similform to Lawson. 1）关于C，需要计算surplus是否≥5%来判断contigent immunization方法是否可以么？contigent immunization指的是当surplus＜5%的时候Passive，当surplus≥5%的时候Active，一个动态的选择过程，那么不论是否≥5%，都可以用contigent immunization策略吧？2）关于surplus的计算Lawson surplus(15498000-14389000)/15498000=7.16%Wharton surplus(8351000-7470000)/8351000=10.55%跟答案里面的7.7%和11.8%不同，是哪里算错了么？

NO.PZ2023032703000035问题如下 Ams anjunior portfolio manager Frank Neeson review the fixeincome portfolios of two new finebenefit plclients, Lawson ors Cabinets, Inc., anWharton Farms. Lawson’s plh30 participants, who are mostly experiencecraftsmen anmachinists, whereWharton hover 100 participants in its plan. The average participant age is 15 years younger for the Wharton plcomparewith the Lawson plan. In both plans, participants receive a monthly benefit upon retirement baseon average finpanhave no option for a lump sum stribution. The two plans’ portfolio characteristiare shown in Exhibit 2.Ams states to Neeson, “For the Lawson anWharton plans, we cconsir one of three alternative strategies to manage the multiple liabilities associatewith these plans. Whenever a plan’s surplus is less th5%, we favor passive management strategies.”Whiof the following three strategies is least likely appropriate for the plans in Exhibit 2? (2019 moAM) A.ration matchingB.Cash flow matchingC.Contingent immunization B is correct. Cash flow matching is least appropriate for both plans. In both the Lawson anWharton plans, participants are entitleto receive a monthly benefit. Cash flow matching entails builng a cateportfolio of zero-coupon or fixeincome bon to ensure there are sufficient cash inflows to pthe schelecash outflows. However, sua strategy is impracticancleto large cash flow holngs between payment tes, resulting in reinvestment risk anforgone returns on cash holngs.C is incorrect. Contingent immunization is appropriate strategy for both plans. Contingent immunization allows for active bonportfolio management until a minimum thresholin the surplus is reache The thresholof 5% (of assets greater thliabilities) is exceein both plans; the Lawson portfolio ha surplus of 7.7%, anthe Wharton portfolio ha surplus of 11.8%.A is incorrect. ration management is also appropriate for both the Lawson anWharton plans. In this case, however, because they enjoy a surplus of assets to liabilities, the contingent immunization strategy is most appropriate. Sinthe plans are in the process of being aisePavoniWharton woullikely aiseto eliminate the ration gin similform to Lawson. 如题，只用ration matching 怎么实现？不是要精准匹配了吗