The contribution margin income statement of Delectable Donuts for May 2018 follows:
DELECTABLE DONUTS
Contribution Margin Income Statement
Month Ended May 31, 2018

Delectable sells five dozen plain donuts for every dozen custard-filled donuts. A dozen plain donuts sells for $4.00, with a variable cost of $1.60 per dozen. A dozen custardfilled donuts sells for $8.00, with a variable cost of $3.20 per dozen.
Requirements
1. Calculate the weighted-average contribution margin.
2. Determine Delectable's monthly breakeven point in dozens of plain donuts and custard-filled donuts. Prove your answer by preparing a summary contribution margin income statement at the breakeven level of sales. Show only two categories of costs: variable and fixed.
3. Compute Delectable's margin of safety in dollars for May 2018.
4. Compute the degree of operating leverage for Delectable Donuts. Estimate the new operating income if total sales increase by 20%. (Round the degree of operating leverage to four decimal places and the final answer to the nearest dollar. Assume the sales mix remains unchanged.)
5. Prove your answer to Requirement 4 by preparing a contribution margin income statement with a 20% increase in total sales. (The sales mix remains unchanged.)

$ 125,000 Net Sales Revenue Variable Costs: $ 32,100 Cost of Goods Sold Selling Costs 17,400 50,000 Administrative Costs 500 75,000 Contribution Margin Fixed Costs: Selling Costs 37,800 Administrative Costs 12,600 50,400 $ 24,600 Operating Income