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.
A product lineâs contribution margin ratio equals the difference between revenues and variable expenses divided by revenues. Itâs the percentage of each productâs revenue that contributes to paying your fixed costs.n a cash basis, divide $5,460 by the new contribution margin percentage of 37.5 percent to compute the required weekly revenue of $14,560, a $2,080 increase. Calculating contribution margin percentage and the BEP tells you what you have to do.