Compute the net area $($Problem $3-12)$

$3-12.$ The $53\frac{1}{2}\frac{1}{2}$ angle shown has one line of $\frac{3}{4}-$in $\frac{O}{?}$ bolts in each leg. The bolts are $3-$in on center in each line and are staggered $1\frac{1}{2}$ in with respect to each other.

FIGURE P$3-12$