The revenue , in dollars, from selling clocks is .

The cost , in dollars, of selling clocks is .

(a)

Find the profit function .

The profit function .

Thus, the profit function is .

(b)

Find the profit if clocks are sold.

The profit function .

Substitute in the profit function.

Thus, the profit if clocks are sold is .

(c)

means that the profit of selling 30 clocks is .

(a) The profit function is .

(b) The profit if clocks are sold is .

(c) means that the profit of selling 30 clocks is .