Answer:
Since the highest paid employees are over age 40, they cannot be simply fired since that would represent age discrimination at work, which is strictly prohibited by the Age Discrimination in Employment Act (ADEA).
But Megan can offer different type of early retirement incentives to these employees so that they retire by their own will, e.g. pay them 1 or 2 weeks salary for every year that they worked for the company, age credits so that the employees can benefit from a pension plan, etc.