In $15\mathrm{.}0$ s$,186$ bullets strike and embed themselves in a wall. The bullets strike the wall perpendicularly. Each bullet has a mass of $5$ x $10^-3$ kg and a speed of $1170$ m$/$s$.($a$)$ What is the average change in momentum per second for the bullets? $($b$)$ Determine the average force exerted on the wall. $($c$)$ Assuming the bullets are spread out over an area of $2\mathrm{.}37$ x $10^-4$ m$^2$ obtain the average pressure they exert on this region of the wall.