In an effort to control selling expenses, the Sell Big Corporation wants to develop a cost volume formula for its selling expenses. An investigation of individual expense items shows

Sales commissions

Fixed

Variable

30% of sales

Advertising

$50,000

Travel and entertainment

30,000

5% of sales

Sales staff salaries

12,000

Depreciation, rent, and insurance sales office

5,000

Determine the cost volume formula in the form of y‘ = a + bx.