Sarah's twist angular momentum increases from $0$ to $50$ Nms in $0\mathrm{.}25$ s as she initiates a twisting jump the ice. During this $0\mathrm{.}25$ s $,$ her moment of inertia about her twist axis is $2\mathrm{.}2k{g}^{**}{m}^2.$

a$.$ How large is the average torque that produces this change in angular momentum?

b$.$ How fast is Sarah's twist angular velocity at the end of the $0\mathrm{.}25$ s $?$