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.
The result will be the current percentage of profit. Calculate the new profit margin by subtracting the new total cost from the current selling price and dividing by the current selling price. Multiply that by 100. The result will be the new percentage of profit given the changes in costs. Subtract the new profit margin from the old profit margin. The difference represents the margin impact of the projected change in costs.