can you please explain specifically how you get Question 3.

PROBLEM 3-16 Cast Behaviour: High-Low Method; Contribution Format Income Statement [LOI , LO26, L03) Skate World is a merchandising company that sells skateboards both at its retail store and its online store. Results for the most recent three months are shown below. July August September Sales in units 4.000 4,500 5,000 Sales S400,000 $450,000 $500,000 Cost of goods sold 240.000 270.000 300,000 Gross margin 160.000 180,000 200,000 Selling and administrative expenses Advertising expense 21.000 21,000 21,000 Shipping expense 34.000 36,000 38,000 Salaries and commissions 78.000 84,000 90,000 Insurance expense 6.000 6,000 6,000 15.000 15.000 15,000 Depreciation expense Total selling and administrative 154.000 162.000 170,000 Operating income S 6,000 $ 18,000 $ 30,000 Required: 1. Identify each of the company's expenses (including cost of goods sold) as either variable, fixed, or mixed. 2. Using the high-low method, separate each mixed expense into variable and fixed elements. State the cost formula for each mixed expense. 3. Redo the company's income statement for September using the contribution format