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.
Deduct the total expenses from the total income, and the profit is $1,500 a month. To calculate the profit rate, divide $1,500 by $3,500 and the result is a profit rate of 43 percent. Profit margin ratio is the ratio of the business's gross profit in relation to sales. Using the example above, your net income is $1,500 a month. Divide this figure by the total income of $5,000 a month, and your percentage of income that constitutes profit is 30 percent.