Mr Brewster operates a roofing company in London and has been asked by the local government authority of Merton to repair the roofs of several of their properties damaged in a recent storm. The job must be completed during the next four weeks (twenty working days), and Merton has offered £16,000 for the job. Mr Brewster has estimated that the job requires seventy-five work days, but he can only use his regular three workers for the job because it is a very busy period for the industry as a whole. Fortunately, Mr Brewster’s son, Will, can take time off from his regular job (paying £80 per day) to help complete the work. Mr Brewster has estimated that, for his regular employees, the cost per work day is £150.