$8-15$ At a point, the normal and shear stresses acting on one plane are $8,000psf$ compression and $2,000psf,$ respectively. On a perpendicular plane, the normal and shear stresses are $2,000$ psf compression and $2,000$ psf$,$ respectively.

$($a$)$ Draw the Mohr's circle.

$($b$)$ Determine the value of the principal stresses.

$($c$)$ Find the angle between the plane on which the $8,000$ psi compressive stress acts and the major principal plane.

$($d$)$ What is the maximum shear stress acting at the point?