Practice: Which firm is maximizing profits? a. By producing one more gadget, it costs a firm in perfect competition an extra $2.00. The selling price per gadget is $3.00. b. By producing one more gadget, it costs a firm in perfect competition an extra $3.00. The selling price per gadget is $5.00. c. By producing one more gadget, it costs a firm in perfect competition an extra $5.00. The marginal revenue per gadget is $3.00. d. By producing one more gadget, it costs a firm in perfect competition an extra $3.00. The selling price per gadget is $3.00