The solid sphere shown in the figure starts from rest and proceeds to roll down the ramp without slipping. The sphere has mass M $=1\mathrm{.}5$ kg and radius R $=6\mathrm{.}0$ cm$.$ The ramp is inclined at angle $=20.($a$)$ What is the sphere$$s translational $($straight$-$line$)$ acceleration? $($b$)$ How much time does it take the sphere to reach a speed of $4\mathrm{.}0$ m$/$s$?($c$)$ How does your answer to part $($b$)$ change if the radius is instead R $=12\mathrm{.}0$ cm$?$