Question

A woman wishes to invest $12,500 in three types of bonds: municipal bonds paying 8% interest per year, bank investment certificates paying 9%, and high-risk bonds paying 12%. For tax reasons she wants the amount invested in municipal bonds to be at least three times the amount invested in bank certificates. To keep her level of risk manageable, she will invest no more than $2500 in high-risk bonds. What is the maximum possible interest yield?

Suppose the investor decides to increase the maximum invested in high-risk bonds to $3500 but leaves the other conditions unchanged. By how much will her maximum possible interest yield increase?