A Machinist Turns on the Power to a Grinding Wheel $38 \mathrm { rad } / \mathrm { s }$

A machinist turns on the power to a grinding wheel at time t = 0 s. The wheel accelerates uniformly from rest for 10 s and reaches the operating angular speed of $38 \mathrm { rad } / \mathrm { s }$ The wheel is run at that angular speed for 30 s and then power is shut off. The wheel slows down uniformly at $2.1 \mathrm { rad } / \mathrm { s } ^ { 2 }$ until the wheel stops. In this situation, what is the angular acceleration of the wheel between $t = 0 \mathrm {~s}$ and $t = 10 \mathrm {~s} ?$

A) 3.8 rad/ $s ^ { 2 }$
B) 4.6 rad/ $s ^ { 2 }$
C) 5.3 rad/ $s ^ { 2 }$
D) 6.1 rad/ $s ^ { 2 }$
E) 6.8 rad/ $s ^ { 2 }$