Which of the following is a variable cost for a company that makes bread?

Data for hermann corporation are shown below: per unit percent of sales selling price $ 125 100 % variable expenses 80 64 contribution margin $ 45 36 % fixed expenses are $85,000 per month and the company is selling 2,700 units per month. required: 1-a. how much will net operating income increase (decrease) per month if the monthly advertising budget increases by $9,000 and monthly sales increase by $20,000? 1-b. should the advertising budget be increased?