Consider for a patient appointment system, a doctor can be scheduled for many appointments, but may not have any scheduled at all. Each appointments is scheduled with exactly 1 doctor. A patient can schedule 1 or more appointments. One appointment is scheduled with exactly 1 patient. An appointment must generate exactly 1 bill, a bill is generated by only 1 appointment. One payment is applied to exactly 1 bill, and 1 bill can be paid off over time by several payments. One patient can make many payments, but a single payment is made by only 1 patient. From this case, the data entities and their attributes required for the patient appointment system: doctor (doc_id, doc_name, physician) , appointment (app_id, app_date, app_time, app_duration, app_reason) , patient (pat_id, pat_name, pat_address, pat_age) , BILL (bill_number, bill_amount, bill_status) , payment (pay_receiptnumber, pay_amount, pay_date, pay_method). Draw a ER diagram for this situation.