Suppose that you invest $1000 into an investment account, interest is compounded quarterly, and you plan to keep this account open for 6 years . (a) Write an equation for the total investment amount, A(r), if interest is compounded at rate r. (b) Find A'(r). What does A'(r) represent? (c) What is the total investment amount after 6 years if the interest rate is 9%? (d) Find A'(0.09). Interpret A' (0.09) in the context of the