Bill's RV Repair Inc. provides repair services for all types of recreational vehicles, including repairs to appliances, heating systems, exterior coverings, and interior features such as tables, storage, and bedding. The repair shop costs include the labour hours for the repair staff; the cost of materials, parts, and supplies; the shop utilities; depreciation of equipment and tools; and the rent on the shop. This is Bill's first year of business. The company's controller is interested in developing a cost function to predict the repair shop costs each month and has collected the following data from the past year on the number of repair jobs and the repair shop costs each month:

Month January February March April May June July August September October November December # of jobs 150 120 125 160 200 240 250 210 195 175 160 155 Repair shop costs $27,500 $22,000 $21,800 $30,000 $36,250 $39,500 $42,300 $37,000 $36,500 $32,700 $28,950 $28,120

Required: a) Using the high-low method, estimate a cost function for repair shop costs. b) Assume that the company controller is attempting to estimate the repair shop costs for February of the next year and has estimated that there will be 135 jobs. What is the estimated repair shop cost, using the formula developed in part a)? c) The controller has just learned that the company's biggest competitor is going out of business, and it is sending all its customers to Bill's RV Repair. The controller estimates that the total jobs for the next month will be 410. Should the controller use the formula developed in part a) to estimate the repair shop cost? Explain.