Answer
$C(x)=120x+12,500$
Work Step by Step
Assuming a linear cost function, $C(x)=mx+b$, where
m represents the marginal cost and
b represents the fixed cost.
Here,
$b$= $?$(fixed cost) and
$m$= $\$ 120$ (the cost to produce one item).
$C(x)=120x+b$
Now, $C(x)=96,500$ when $x=700$.
We don't know $b$, but we were given $C(700)=96,500$,
so we solve (for $b$):
$120(700)+b=96, 500$
$84,000+b=96, 500$
$b=12, 500$
$C(x)=120x+12,500$
