Assume that if the shear stress in steel exceeds about 4.00 108 N/m2, the steel ruptures.

(a) Determine the shearing force necessary to shear a steel bolt 1.40 cm in diameter.

(b) Determine the shearing force necessary to punch a 1.75-cm-diameter hole in a steel plate 0.690 cm thick.
N

Got A just don't understand B