1. The problem statement, all variables and given/known data Estimate the change in volume of carbon dioxide if 'r' is increased from 10 to 11 (10% increase). Assume 30 million cars, all use 1m^3 of fuel each year 2. Relevant equations Efficiency of an Otto Cycle η=1-r^(1-gamma) 3. The attempt at a solution Original η=1-10^(1-gamma) Final η=1-11^(1-gamma) I then looked up a typical value of gamma (1.3), and worked out the efficiency of each Original = 0.4988 Final = 0.5129 Not sure if this is right, as you weren't given the value of gamma. Then I'm not entirely sure how to work out how much CO2 is produced from each m^3 of fuel, is it just multiplying by the efficiency? Or have I gone completely wrong?