Draper Automotive started business in April 2011. Since opening a couple of years ago, they have been

Question:

Draper Automotive started business in April 2011. Since opening a couple of years ago, they have been able to serve some people more than once as they come back for repeat service and additional work. Dawn Draper is in charge of all the scheduling of jobs, billing, and customer relations. In the last 6 months, Dawn has received a number of complaints from customers about the billing. Strangely, however, she would receive a flurry of complaints in one month, then cards and thank-you notes the next month. She does the billing the same way every month, so she can't understand the fluctuations in satisfaction levels.
The process for the billing is to start with the cost of the automotive parts used in the repair or upgrade. These costs are taken from the purchase order price lists from the suppliers. To the amount for the parts is added a labour amount. The labour amount is calculated so that it includes the cost of the mechanics' labour ($25) plus an amount for overhead. The amount for overhead is the previous month's actual overhead amount divided by the estimated number of jobs for the upcoming month. Dawn's estimations for the number of upcoming jobs is usually pretty good.
Peggy Olsen came to see Dawn today to complain about the billing. She brought in two invoices. One from 5 months ago and one from a week ago. Both were for oil and filter changes. The invoices are below:

Once Dawn saw them side by side, she knew there was a problem, but since she was working from actual numbers for the overhead, she wasn't sure what could be done. She knew that if something didn't change they would begin to lose customers, so she went through her records to see if she could see where any mistakes were made. Dawn summarized the last 6 months' overhead calculations as follows: