Two friends take a 3000-mile cross-country trip together, but they drive their own cars. Car A has a 12-gallon gas tank and averages 40 miles per gallon, while car B has a 20-gallon gas tank and averages 30 miles per gallon. (Assume both drivers pay $2.55 per gallon of gas.) 

a) What is the cost of one tank of gas for each car ? 

b) How many tanks of gas does each car use for the trip? 

c) How much does each driver pay for gas for the trip ?