Which of these statements is (are) correct? Assume a constant, positive, annual rate of interest. (Select all that apply.)
a) The present value of a future sum decreases as the interest rate increases.
b) The future value of a present sum decreases as the interest rate increases.
c) The present value of a future sum increases as the interest rate increases.
d) The future value of a present sum increases as the interest rate increases.
