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.
Step 2. Calculate your contribution margin in dollars per unit. Once you know the selling price and direct costs of each product or service unit you sell, you can calculate your contribution margin in dollars per unit. This is the amount of money you get over and above your direct costs for each unit you sell.