The 20 -kg motor has a center of gravity at $G$ and is pin connected at $C$ to maintain a tension in the drive belt. Determine the smallest counterclockwise twist or torque $\mathbf{M}$ that must be supplied by the motor to turn the disk $B$ if wheel $A$ locks and causes the belt to slip over the disk. No slipping occurs at $A$. The coefficient of static friction between the belt and the disk is $\mu_{x}=0.3$.