In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.
Q: Carol Hathaway: Is something wrong ?
Dr. Peter Benton: Oh , you bet there is . We 're out of coffee again because the nurses have been taking it , that 's what 's wrong .
Carol Hathaway: So make some more .
Dr. Peter Benton: Make some more ? We work 36 hours on , _ 18 _ off , which is 90 hours a week , 52 weeks a year . For that , we are paid $ 23739 before taxes , and we also have to * make * the coffee ?
Carol Hathaway: My heart is breaking .
A:
hours