Identify each expense as fixed variable or mixed and

Question

Mighty Bright Window Cleaners" monthly income statement at several levels of activity is as follows:

Windows washed	2,000	4,000	6,000
Sales	$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
Advertising	400	400	400
Salaries and wages	700	900	1,100
Insurance	200	200	200
Postage	400	800	1,200
Total operating expenses	1,700	2,300	2,900
Operating income	$ 100	$1,300	$2,500

Required

1. Identify each expense as fixed, variable, or mixed.
2. Prepare a contribution margin income statement based on a volume of 5,000 windows.