Darnell drives about 15,000 miles each year. He is planning to buy a new car. The car he wants to buy averages 20 miles on one gallon of gasoline. He has decided he would buy another car if he could save at least $200 per year in gasoline expenses. Assume gasoline costs $1.20 per gallon. What is the minimum number of miles per gallon that would fulfill Darnell's criteria?