In a market economy, the real power in the market place is held by the

The two main types of managed care organizations are:

A. U.S. veterans' hospitals and university health clinics. B. health maintenance organizations (HMOs) and private nursing homes. C. health maintenance organizations (HMOs) and preferred provider organizations (PPOs). D. preferred provider organizations (PPOs) and nonprofit hospitals.

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

A) $2.50. B) zero. C) $2.00. D) 50 cents.