Example 3

A new plumber has just started his own business. In order to try and gain customers, he is running a special for his services. He charges $16 per hour, plus a standard house call fee of $25. Determine the slope of the line that passes through the points of the total cost for jobs lasting from 2 hours to 6 hours. Explain what the slope means in the context of the problem. Finally, use the slope to determine how many hours of work a customer could get for $150. Assume there is no sales tax.