$($a$)$ Set up the element at point $A$ on the solid shaft in Figure and indicate the magnitude and directions of stresses due to the applied loading, $($b$)$ Determine the magnitudes and directions of the principal stresses and maximum shearing stresses acting at this point, $($C$)$ Use Mohr's circle to find the direction and magnitudes of the principal stresses and maximum shearing stress at point $A$