Suppose that an account pays interest at an annual rate r compounded m times per year and that a withdrawal of size P is made at the beginning of each compounding interval (an annuity-due). Let Aen...

Suppose that an account pays interest at an annual rate r compounded m times per year and that a withdrawal of size P is made at the beginning of each compounding interval (an annuity-due). Let Aen denote the value of the account at time n, that is, just before the nth withdrawal. (See figure.)