Answer
The magnitude of the torque is $~50~N \cdot m$
Work Step by Step
The angular impulse is equal to the change in angular momentum. We can use the change in angular momentum to find the torque:
$\tau~t = \Delta L$
$\tau = \frac{L_f-L_0}{t}$
$\tau = \frac{(115~kg~m^2/s)-(240~kg~m^2/s)}{2.5~s}$
$\tau = -50~N \cdot m$
The magnitude of the torque is $~50~N \cdot m$.
