$[2$ points$]$ Your monthly car payment in dollars is described by the function $P=f(P_0,r),$ where $P_0$ dollars is the amount you borrowed and $r$ percent is the interest rate. As an example, if you borrow $$20,000$ for $60$ months at $3\mathrm{.}9\%,$ then your monthly payments could be given by the value $P=f(20000,0\mathrm{.}039)=367$ dollars.

a$.$ Is $\frac{\text{d}\text{e}\text{l}\text{P}}{del{P}_0}$ positive or negative?

b$.$ Is $\frac{\text{d}\text{e}\text{l}\text{P}}{\text{d}\text{e}\text{l}\text{r}}$ positive or negative?