Two steel plates are fastened together using four bolts. The bolts each have a shear modulus of 80 GPa and a shear strength of 600 MPa. The radius of each bolt is 1.0 cm. Normally, the bolts clamp the two plates together and the frictional forces between the plates keep them from sliding. If the bolts are loose, then the frictional forces are small and the bolts themselves would be subject to a large shear stress. What is the maximum shearing force F on the plates that the four bolts can withstand?