Shown here is an income statement in the traditional format for a firm with a sales volume of 18,000 units: Revenues $183,668 Cost: of goods sold ($18,866 + $2.86lunit] 68,468 Gross profit: 5. 4?,568 Operating expenses: Selling ($2,266 + $1.68lunit) 28,268 Administration ($5,666 + $6.48/unit) 12,268 Operating income $ 15,268 [ Required: a. Prepare an income statement in the contribution margin format. In. Calculate the contribution margin per unit and the contribution margin ratio. c. Calculate the firm's operating income [or loss} if the volume changed from 18,000 units to 1. 20,000 units. 110,000 units. d. Refer to your answer to part a when total revenues were $108,000. Calculate the firm's operating income [or loss} if unit selling price and variable expense per unit do not change and total revenues 1. Increase by $15,000. 2. Decrease by $10,000