Answer
$\$5,446.38$
Work Step by Step
By Heron's formula, the area of a triangle with sides $a,b$ and $c$ is given by:
$K=\sqrt{s(s-a)(s-b)(s-c)}$;
where $s=\dfrac{a+b+c}{2}$
Therefore, $s=\dfrac{100+50+75}{2}=112.5$
and
$K=\sqrt{112.5(112.5-100)(112.5-50)(112.5-75)}\approx 1815.46$
The unit price is $\$3$ per square foot. So, we will multiply the area and the cost per square foot to get the total cost.
Thus, $\$3 \times (1815.46)=\$5,446.38$
