The Central Valley Company is a merchandising firm that sells a single product. The companys revenues and expenses for the last three months are given below: Central Valley Company Comparative Income Statement For the Second Quarter April May June Sales in units 4,300 5,100 6,200 Sales revenue $ 640,700 $ 759,900 $ 923,800 Cost of goods sold 236,500 280,500 341,000 Gross margin 404,200 479,400 582,800 Selling and administrative expenses: Shipping expense 60,000 66,880 76,340 Advertising expense 66,000 66,000 66,000 Salaries and commissions 134,000 152,400 177,700 Insurance expense 6,000 6,000 6,000 Depreciation expense 34,000 34,000 34,000 Total selling and administrative expense 300,000 325,280 360,040 Net operating income $ 104,200 $ 154,120 $ 222,760 Required: a. Determine which expenses are mixed and, by use of the high-low method, separate each mixed expense into its variable and fixed components. State the cost formula for each mixed expense. (Round "per unit" answers to 2 decimal places. Omit the "$" sign in your response.) Cost formula $ ***** +**** $ ***** per unit $ **** + **** $ ***** per unit b. Compute the companys total contribution margin for May. (Round your answer to the nearest whole number. Omit the "$" sign in your response.) Contribution margin $ ***** I need the *'s filled in. Any help would be greatly appreciated