The angular velocity of a rotating rigid body increases from $650$ to $1,900$ rev$/$min in $135$ s$.($Enter the magnitudes.$)$

$($a$)$

What is the angular acceleration of the body $($in rad$/$s$2)?$

rad$/$s$2$

$($b$)$

Through what angle $($in rad$)$ does it turn in this $135$ s$?$

rad