The net profit form the sale of a product is equal to the total revenue from the sales of that product minus the total cost for the sale of that product. If a particular model of laptop sells for $ \$ 350$ and the cost of making and selling $n$ of these laptops is $ \$(30 n + 12,000) $ the equation which expresses the net profit in dollars $P$, for making and selling $n$ of these calculators is

Question

$\begin{array}{1 1} (a)\; 320 n - 12,000 \\(b)\; 330 n - 12,000 \\ (c)\; 320 n + 12,000 \\ (d)\; 330 n + 12,000 \end{array}$