Mighty Bright Window Cleaners' monthly income statement at several levels of activity is as follows: Windows washed 1,000 2,000 3,000 Sales revenue $ 3,000 $ 6,000 $ 9,000 Cost of goods sold 1,200 2,400 3,600 Gross profit 1,800 3,600 5,400 Operating expenses 400 400 400 Advertising expense Salaries and wages expense 700 900 1,100 Insurance expense 200 200 200 Postage expense 400 800 1,200 Total operating expense 1,700 2,300 2,900 Operating income ta 100 $ 1,300 $ 2,500 (b) Prepare a contribution margin income statement based on a volume of 2,500 windows. (Round unit cost to 2 decimal places, e.g. 52.75 and all other answers to O decimal places, eg. 5,275.) 2,500 windows Per Unit Sales Revenue $ 7500 Variable Expenses Cost of Goods Sold 3000 i 1.20 i Salaries Expense Postage Expense Total Variable Expenses 4500 DO Contribution Margin 3000 Fixed Expenses : Salaries Expense | Insurance Expense 200 i Advertising Expense Total Fixed Expenses 1100 i Operating Income 1900