4. A flat bar of width b = 60 mm and thickness t = 10 mm is loaded in tension by a force P (see figure). The bar is attached to a support by a pin of diameter d that passes through a hole of the same size in the bar. The allowable tensile stress on the net cross section of the bar is 140 MPa, the allowable shear stress in the pin iss 80 MPa, and the allowable bearing stress between the pin and the bar is σ = 200 MPa. (a) Determine the pin diameter do for which the load P will be a maximum. (b) Determine the corresponding value Pmax of the load. ΟΙ P Figure 4 P