Waterways has a sales mix of sprinklers, valves, and controllers as follows. Unit variable manufacturing costs: Unit variable selling and administrative expense for: Determine the sales mix based on unit sales for each product. Attempts: unlimited (b) Using the annual expected sales for these products, determine the weighted-average unit contribution margin for these three products. (Round answer to 2 decimal places, es 5,25.) Weighted-Average Unit Contribution Margin $