a$)$ A $115$kg stretcher is pushed, starting from rest, and a maximum veolcity of $4\mathrm{.}0$ m$/$s is reached over a time of $15$s$.$ How much force was applied?

b$)$ if the force in a$.$ Was applied over $7\mathrm{.}5$m$.$ How much force was done and how much power was used?