If an industry consisting of two firms produces a total of 12 units, the market price is $10. If 13 units are produced, the price falls to $9. Suppose the two firms form a cartel and agree to produce 6 units each. If one firm cheats and produces 7 units, the cheating firm's revenue rises by and the noncheating firm's revenue falls by a) $3; $12 b) $6: $12 c) $6: $6 d) $3: $6