A conveyer bell is used to transfer granular material and the frictional resistance on the...

A conveyer bell is used to transfer granular material and the frictional resistance on the lop of the belt is F = 500 N. Determine the smallest stretch of the spring attached to the moveable axle of the idle pulley B so that the bell does not slip at the drive pulley A when the torque M is applied. What minimum torque M is required to keep the belt moving? The coefficient of static friction between the belt and the wheel at A is µs = 0.2.