GMAT Quantitative Reasoning Practice Test 3

M.A.S (Most Affordable Speed) is defined as the speed where the fuel consumption of a car is the lowest. The average family car consumes 3 liters of fuel per 36 kilometers at the M.A.S with only one passenger (the driver). A pickup truckconsumes twice as much as a family car does. Assuming the fuel consumption of both cars rises by % of the original consumption for each additional passenger, how many km per litter would a pickup truck do if the driver has three additional passengers?