The pollution level near a dump site has been modeled by the equation $,$ P$($t$)=0\mathrm{.}05+0\mathrm{.}12$e$^0\mathrm{.}38$t where is the volume of pollutants $($in cubic meters$)$ and is the time $($in years$).$ a$)$ What is the rate change in the pollution level with respect to time?