You are working as a forensic accountant for a law firm that has been hired by a company to investigate possible fraudulent activity by one of their employees. The employee, who is responsible for processing invoices, is suspected of creating fake invoices and pocketing the money for personal use. Your investigation reveals that the employee created 20 fake invoices over the past six months, totaling $50,000.

a) Calculate the average amount of each fake invoice.

b) Based on the average amount of each fake invoice, estimate the total amount of fake invoices that the employee may have created over the past two years.

c) The employee was paid a salary of $60,000 per year. Assuming that the employee only created fake invoices during work hours, estimate the percentage of the employee's salary that was earned through fraudulent activity over the past two years.