3. A steel pipe of 60-mm outer diameter is to be used to transmit a torque of 350 N. m without exceeding an allowable shearing stress of 12 MPa. A series of 60-mm outer diameter pipe is available for use. Knowing that the wall thickness of the available pipes varies from 4 mm to 10 mm in 2-mm increments, choose the lightest pipe that can be used. O 60 mm

Fig: 1