Please solve $6\mathrm{.}22$

$6\mathrm{.}22$ For the beam and loading shown, consider section $\backslash ($ n$-$n $\backslash )$ and determine the shearing stress at $($a$)$ point $\backslash ($ a $\backslash ),($b$)$ point $\backslash ($ b $\backslash ).$

Fig. P$6\mathrm{.}21$ and P$6\mathrm{.}23$

rig. ro$.\backslash (\backslash$angle$<mtext></mtext><mi>\backslash </mi><mi>)</mi>$ and ro$.\backslash (\backslash$angle $4\backslash )$