=+f. Suppose an increase in gasoline taxes raises the opportunity cost of driving a mile with a fuel-efficient car to the opportunity cost of driving a gas guzzler before the tax increase. Will someone who was previously indifferent between a fuel-efficient and a gas-guzzling car now drive more or less in a fuel-efficient car than he did in a gas guzzler prior to the tax increase?

(Continue with the assumption that tastes are homothetic.)