Maria wishes to buy gasoline and have her car washed. She finds that if shebuys 9 gallons of gasoline at $2.

Maria wishes to buy gasoline and have her car washed. She finds that if shebuys 9 gallons of gasoline at $2.50 per gallon, the car wash costs $2, but ifshe buys 10 gallons of gasoline, the car wash is free. For Maria, the marginalcost of the tenth gallon of gasoline and car wash is