7. Suppose a man can invest his money of $90000 in three funds. Fund A has a rate of return of 3%, fund B has a rate of return of 4.5%, fund C has a rate of return of 5%. (a) If he only invests in fund A and B, how much should he invest in each fund to get a rate of return of 4%? (b) If he only invests in fund A and C, how much should he invest in each fund to get a return $4050? (c) If he could invest in any fund, come up with a plan (how much to invest in A, B, C respectively) that will yield a rate of return of 3.5%