Suppose two firms operate under a system of marketable pollution permits. If it costs Firm A $25 to reduce pollution by 1,000 units per day, and Firm B can reduce costs by $35 by increasing pollution by 1,000 units per day
a. the firms cannot gain by trading the right to pollute.
b. both firms can benefit if Firm A trades the right to pollute 1,000 units to Firm B for $30.
c. both firms can benefit if Firm A trades the right to pollute 1,000 units to Firm B for $40.
d. both firms can benefit if Firm B trades the right to pollute 1,000 units to Firm A for $30.