Eastwood Music uses flexible budgets to control its selling expenses. Monthly sales are expected to be from $400,000 to $450,000. Variable costs and their percentage relationships to sales are: Sales commissions Advertising Traveling Delivery 8% 5% 15% 2% Fixed selling expenses consist of sales salaries of $50,000, and depreciation on stage and production equipment totaling $12,000. Required: Prepare a flexible budget for $420,000 of sales