Hello, people. I have some questions on SOA FM sample questions. This is SOA FM-09-15.

On comparing problem 71 and 128 which are full immunization problems, the solution manual took different approaches on the two. On 71, it solved through using [L][/t], [A][/t], and t. But on 128, it solved through using derivative. Can someone why the manual used different approaches on the two questions?

On problem 132, I did not understand how the solution manual listed the combined cost of the bonds yet disregarded it at the end. Can someone explain it for me?

If you need the questions, I can put them on later on.

Thank you