Question a) Given the keys in a relational table below, briefly explain each of them with an example. i . Primary key ii. Foreign Key iii. Candidate key (9 marks) b) Using the Chen or Crow foot notation methodology, create an ERD that can be implemented for a medical clinic, using at least the following business rules: A patient can make many appointments with one or more doctors in the clinic, and a doctor can accept appointments with many patients. However, each appointment is made with only one doctor, and each appointment references a single patient Emergency cases do not require an appointment. However, for appointment management purposes, an emergency is entered in the appointment book as "unscheduled." If kept, an appointment yields a visit with the doctor specified in the appointment. The visit yields a diagnosis and, when appropriate, treatment. With each visit, the patient's records are updated to provide a medical history Each patient visit creates a bill. Each patient visit is billed by one doctor, and each doctor can bill many patients. Each bill must be paid. However, a bill may be paid in many installments, and a payment may cover more than one bill. A patient may pay the bill directly, or the bill may be the basis for a claim submitted to an insurance company. If an insurance company pays the bill, the deductible is submitted to the patient for payment