Answer
$\$119$
Work Step by Step
Substituting $x$ with $
50
$ in $C(x)=\dfrac{35x+4200}{x}$, then,
\begin{array}{l}\require{cancel}
C(50)=\dfrac{35(50)+4200}{50}
\\\\
C(50)=\dfrac{5950}{50}
\\\\
C(50)=119
.\end{array}
Hence, the average cost is \$119.