The drive shaft AB of an automobile is made of a steel having an allowable shear stress

Question:

The drive shaft AB of an automobile is made of a steel having an allowable shear stress of Ï„_allow= 8 ksi. If the outer diameter of the shaft is 2.5 in. and the engine delivers 200 hp to the shaft when it is turning at 1140 rev>min, determine the minimum required thickness of the shaft€™s wall.