The Central Valley Company is a merchandising firm that sells a single product. The company's revenues and expenses for the last three months are given below: AprilMayJune 4,500.. 5,250- e 6,000- Sales in units Sales revenue $630,000 $735,000 $840,000. Gross Margin Less operating expenses: ..378,000441,000504,000 9 Shipping expense 56,00063,50071,000 70,000-e 70,000 70,000? 143,000161,750180,500 9,000 9,0009,000 42,00042,00042,000 320,000.346,250372,500 $58,000 $94,750 $131,500 Total operating expenses Net income.. Required: Determine which expenses are mixed (show computations) 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. a. b. Compute the company's total contribution margin (Sales-Variable Costs) for May