Problem $5-$ Friction

$\frac{6}{3}$ The force $P$ is applied to the $50-kg$ block when it is at rest. Determine the magnitude and direction of the friction force exerted by the surface on the block if $($a$)P=0,($b$)P=200N,$ and $($c$)P=250N.($d$)$ What value of $P$ is required to initiate motion up the incline? The coefficients of static and kinetic friction between the block and the incline are ${}_s=0\mathrm{.}25$ and ${}_k=0\mathrm{.}20,$ respectively.

PROBLEM $6/3$