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.
To solve for this equation, you first need to solve for the contribution margin, which is revenue minus variable expenses. If a company has $100 in revenue from sales and $30 in variable expenses, then its contribution margin is $100 - $30 = $70.In this case, the contribution margin ratio is $70 / $100 = .70. Multiply .70 by 100 to change the decimal into a percentage and you get 70 percent.f a company has $100 in revenue from sales and $30 in variable expenses, then its contribution margin is $100 - $30 = $70. In this case, the contribution margin ratio is $70 / $100 = .70. Multiply .70 by 100 to change the decimal into a percentage and you get 70 percent.