Workco must have the following number of workers available during the next three months: month 1, 20; month 2, 16; month 3, 25. At the beginning of month 1, Workco has no workers. It costs Workco $100 to hire a worker and $50 to fire a worker. Each worker is paid a salary of $140/month. Formulate the problem of determining a hiring and firing strategy that minimizes the total cost incurred during the next three months as a MCNF problem.