Answer: b, since that price will induce firm X top buy three permits and firm Y to buy 1 permit. A. $400 b. $500 c. $600 d. $700 e. none of the above will result in the desired pollution reduction. Among the following prices for each one-ton-per-day pollution permit, which is the smallest the government could charge if its goal were to cut total pollution in half? A. $400 b. $500 c. $600 d. $700 e. none of the above will result in the desired pollution reduction.