Which one of the following statements is correct, all else constant? The present value of a sum is not affected by the interest rate. (B) The present value of a sum increases as the period of time increases. The future value of a sum is not affected by the interest rate. The future value of a sum increases as the period of time increases. E Because time is the exponent in the present value formula, the length of an investment period has minimal effect on the present value of the investment