During a $4\mathrm{.}9$ s time interval, a flywhed with a constant angular acceleration turns through $573$ radians and acquires an angular velocity of $156$ rad$/$s$.($Assume the flywheel is rotating in the positive direction. Indicate the direction with the signs of your answers.$)$

$($a$)$ What is the angular velocity $($in rad$/$s$)$ at the beginning of the $4\mathrm{.}9$ s $?$

$ra\frac{d}{s}$

$($b$)$ What is the angular acceleration of the flywheel $($in rad$/$s $s^2)?$

$ra\frac{d}{s^2}$