The first programming project involves writing a program that computes the average salary for a collection of employees of different types. This program consists of four classes. The first class is the Employee class, which contains the employee's name and monthly salary, which is specified in whole dollars. It should have two methods:

1. A constructor that allows the name and monthly salary to be initialized.
2. A method named annualSalary that returns the salary for a whole year.

The Employee class has two subclasses. The first is Salesman. It has an additional instance variable that contains the annual sales in whole dollars for that salesman. It should have the same two methods:

1. A constructor that allows the name, monthly salary and annual sales to be initialized.
2. An overridden method annualSalary that returns the salary for a whole year. The salary for a salesman consists of the base salary computed from the monthly salary plus a commission. The commission is computed as 2% of that salesman's annual sales. The maximum commission a salesman can earn is $20,000.

The second subclass is Executive. It has an additional instance variable that reflects the current stock price. It should have the same two methods:

1. A constructor that allows the name, monthly salary and stock price to be initialized.
2. An overridden method annualSalary that returns the salary for a whole year. The salary for an executive consists of the base salary computed from the monthly salary plus a bonus. The bonus is $30,000 if the current stock price is greater than $50 and nothing otherwise.

Finally there should be a fourth class than contains the main method. It should create an array of objects of type Employee and initialize them to a mixture of different kinds of employees. It should then compute and display the average salary for all employees.

Be sure to follow good programming style, which means making all instance variable private and naming all constants. Furthermore you must select enough different kinds of employees to completely test the program.