An expert is analyzing the cost behavior patterns of the defendant in an antitrust dispute. The expert plans to use the information to prepare a damage estimate. The expert analyzed $30$ months of cost and sale data for the Downtown Department Store. The results of regression$-$correlation analyses on the store$$s six cost categories regressed against sales dollars are as follows:

$\backslash$table$[[$Account$,$a value,b value,r squared$],[$Cost of goods sold,$$45,000,\mathrm{.}46,\mathrm{.}88],[$Store salaries,$$65,000,\mathrm{.}055,\mathrm{.}72],[$Store utilities,$$26,000,\mathrm{.}015,\mathrm{.}34],[$Store maintenance,$$14,000,\mathrm{.}08,\mathrm{.}035],[$Advertising$,$$$26,000,\mathrm{.}01,\mathrm{.}001],[$Corporate overhead,$$75,000,\mathrm{.}025,\mathrm{.}045]]$a$.$ Use the cost behavior data presented above to make a point estimate of expected costs and net income for the month of July $($assuming sales of $$980,000).$

b$.$ How would you describe $($categorize$)$ each of the costs?

c$.$ How strong do you feel about estimations you made in part a$?$