A database is needed to keep track of the operations of a physical therapy center. Every patient must be referred by a physician and have a prescription flr physic therapy in order to recieve treatments. A patient may have different physicians at different times. The database keeps all information about prescription and treatments, both past and current. When appointments are made, the information about scheduled date and time is recorded. No patient is ever scheduled for two visits on ome day. The center has several physical therapists on different visits. When a patient makes a visit at an appointed time, the name of the therapist, the treatment, the date, the time, and the equipment used are all recorded for that visit. Each of these has only one value for the visit. This information will be used later for insurance billing, which is not part of this database. Draw a complete E-R diagram for this example.