You are to create a solution for a Pharmaceutical company.

Entities to be represented are: Drugs, Sales Representatives, Bills and Vouchers.

A Drug is characterized by its name (string), its price (int) and its manufacturer (a manufacturer ==> composition).

A Manufacturer is characterized by his name (string) and the list of drugs they sell (array of drugs) ==> composition.

A Sales Representative (sometimes referred to as rep) is characterized by his/her name(string), the total amount sold (double), his/her salary (int).

* Sales Representatives can be of two types (inheritance):

Reps with a fixed income and a commission

Reps with a commission only

A Voucher is characterized by its number (int), a client name (a customer), and the quantity sold of each drug.

All reps and vouchers and bills are payable. As such, students need to implement an interface called Payable and implement it in the aforementioned classes.

1. You need then to create GUI interfaces where the user can manage all entities and then be able to generate a report showing the vouchers one after the other and how much as well as the total of each.

2. The user should be able to search for the vouchers of a certain customer.

3. Your GUI should also allow showing how much each rep has sold up till now and as such how much he/she has earned.

4. The system should tell which vouchers are still unpaid and how much their total is.

5. The system should allow the user to navigate between the different instances of the entities.