In the Preferred Provider Organization (PPO) type managed care plan which of the following is (are) true?1) Physicians remain in their own offices but contract to treat patients enrolled in the plan2) Health plan contracts with physicians to provide care according to a discounted fee schedule3) Physicians may contract with more than one managed care plan and can see other patients on a fee-for-service basis4) Plans generally do not use primary care physicians as gatekeepers5) All of the above6) None of the above