1 Onset of sleep from time the lights were turned off; this is called  sleep onset latency  and normally is less than 20 minutes. ( 2 Note that determining sleep and awake is based solely on the EEG. Patients sometimes feel they were awake when the EEG shows they were sleeping.
The direct cost margin is calculated by taking the difference between the revenue generated by the sale of goods or services and the sum of all direct costs associated with the production of those goods, divided by the total revenue.
We use the contribution margin ratio to do this. Using the same example, variable expenses of $0.80 are 40% of sales of $2.00 per unit ($0.80/$2.00). To calculate breakeven in dollars, divide its fixed expenses by the contribution margin ratio of 60% ($60,000/.6 = $100,000).This means that the company has to make $100,000 in sales to breakeven. The contribution margin ratio is an important financial metric to calculate the profit potential for a business firm.If the dollar amount of sales increases by one dollar, in this example, the contribution margin increases by 60 cents.he contribution margin ratio is an important financial metric to calculate the profit potential for a business firm. If the dollar amount of sales increases by one dollar, in this example, the contribution margin increases by 60 cents.