Consider a Function of Three Variables $P = f ( A , r , N )$

Essay

Consider a function of three variables $P = f ( A , r , N )$ , where $P$ is the monthly mortgage payment in dollars, $A$ is the amount borrowed in dollars, $r$ is the annual interest rate, and $N$ is the number of years before the mortgage is paid off.(a) Suppose $f ( 180,000,6,30 ) = 1080$ . What does this tell you in financial terms?
(b) Suppose $\frac { \delta f } { \delta r } ( 180,000,6,30 ) = 115.73$ . What does this tell you in financial terms?
(c) Suppose $\frac { \delta f } { \delta N } ( 180,000,6,30 ) = - 12.86$ . What does this tell you in financial terms?