The hospital uses regular nurses, part$-$time nurses $($when the hospital can get them$),$ and contract nurses $($who are not employees$).$ Contract nurses work a number of hours, which varies depending on their contract with the hospital. Regular nurses are paid a sum of $$15,000$ per quarter for $60$ days of work; part$-$time nurses are paid $$6500$ per quarter for $30$ days of work. Contract nurses get an average of of $$17,200$ per quarter for $60$ days of work. It costs $$1000$ to hire or lay off any of these three types of nurses.