Stress Analysis $[25$ pts$].$ A steel tap wrench is used to tap pre$-$drilled holes with the shown forces. Structural properties at section A are given below. The material is ductile, and therefore stress concentrations can be neglected.

a$.$ Draw an arrow that clearly indicates the location of the critical stress element at section A in the figure above for any value of P$.[3$ pts$]$

b$.$ If $P=10lbf,$ calculate the normal and shear stresses at the critical stress element $($sketch these stresses on the $3$D stress element$)$ and determine the factor of safety if using maximum shear stress $($MSS$).[14$ pts$]$