#### Answer

$C(x)=45x+35$

#### 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= $\$ 35$ (fixed cost) and
m= $?$ (the cost to produce one item).
Let $C(x)=$ cost of producing $x$ items.
$C(x)=mx+35$
We don't know m, but we were given $C(8)=395$ ,
so we solve (for m):
$m(8)+35=395$
$8m=360\qquad/\div 8$
$m=45$.
$C(x)=45x+35$