Shirrell Blackthorn is the accountant for several pizza restaurants based in a tri-city area. The president of the chain wanted some help with budgeting and cost control, so Shirrell decided to analyze the accounts for the past year. She divided the accounts into four different categories deepening on whether they appeared to be primarily fixed or to vary with one of three different drives. Food and wage costs appeared to very with the total sales dollars. Delivery costs varied with the number of miles driven (workers were required to use their own cars and were reimbursed for miles driven). A group of other costs, including purchasing, materials handling. and purchases of kitchen equipment, dishes, and pans appeared to very with the number of different product types (e.g.. pizza, salad, and lasagna). Shirrell came up with the following monthly average