Mark Corporation produces two models of calculators. The Business model sells for $40, and the Math model sells for $20. The variable expenses are given below:

Business
Model
Math
Model
Variable production costs per unit $16 $17
Variable selling and administrative expenses per unit $ 8 $ 5

The fixed expenses are $76,000 per month. The expected monthly sales of each model are: Business, 1,100 units; Math, 600 units.

The contribution margin ratio for the Business model is: (Do not round intermediate calculations.)
56%
20%
44%
40%