Answer
The fixed cost is $\$1200$
The variable cost is $\$1500$
The marginal cost is given, $\$1500$.
Work Step by Step
As we saw in exercise a., the daily cost function is:
$C(x)=1500x+1200$
The fixed cost is $\$1200$, because we have to pay it whether we want to manufacture only 1 piano or 12 pianos.
The variable cost is $\$1500$, as it varies with the number of piano we manufacture.
The marginal cost is given, $\$1500$.
