Solve this problem using Mohr's Circle

$7\mathrm{.}9$ through $7\mathrm{.}12$ For the given state of stress, determine $($a$)$ the orientation of the planes of maximum in$-$plane shearing stress, $(b)$ the maximum in$-$plane shearing stress, $($c$)$ the corresponding normal stress.

Fig. P$7\mathrm{.}7$ and P$7\mathrm{.}11$

Solve this problem using Mohr's Circle