P$19\mathrm{.}11$ Consider the following mechanism, which results in the formation of product $P$ :

$A{}_{k_{-1}}^{k_1}B{}_{k_{-2}}^{k_2}C$

$B{k}_{3}P$

If only the species $A$ is present at $t=0,$ what is the expression for the concentration of $P$ as a function of time? You can apply the preequilibrium approximation in deriving your answer.