3. Determine whether the following statements are true or false. Explain your answers.

a. A firm will make a profit when the price it charges exceeds the average variable cost of the chosen output level.

b. To maximize profits in the short run, a firm must minimize its costs.

c. If economic profit is positive, firms will exit the market in the short run.

d. A firm that receives a price greater than its average variable cost but less than its average total cost should shut down.