A dentist's drill starts from rest. After $3\mathrm{.}20$ s of constant angu$-$lar acceleration, it turns at a rate of $2\mathrm{.}51\backslash$times $101$ rev$/$min$.($a$)$ Find the drill's angular acceleration. $($b$)$ Determine the angle$($in radians$)$ through which the drill rotates during this period.