The Valley Company is a merchandising firm that sells a single product. The company's revenues and expenses for the last three months are presented below: VALLEY COMPANY Comparative Income Statement for the Second Quarter 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. b$.$ Compute the company's total contribution margin for May. With explanation please.