3. An 8-inch diameter steel shaft is force fit into a cast iron disk with a 20-inch outside diameter. The maximum tangential stress in the disk is 5000 psi. If Esteel = 30x106 psi and Ecast iron = 15x106 psi, with Poisson’s ratio  for both materials equals to 0.3, (a) Determine the contact pressure required between the shaft and the disk (A: p  3621 psi ). (b) Determine the decrease in the radius of the shaft (A: ds = 0.00034 inch). (c) Determine the required diametral interference (A: 2 = 004 in. (Hint: A change in the shaft radius or diameter can be obtained through the displacement in the shaft)