Answer to Question 1
Full-and part-employees have similar needs to work a desired number of hours to attain personal financial goals. At the same time, the restaurant manager has an obligation to control labor costs. Though all staff members are valuable to the restaurant (if they were not, they wouldn't have been employed), most restaurant managers do not want to lose their best and most valued full-time staff members. Some managers use an on-call system in which they have access to persons willing to work a few shifts once in a while and use of this tactic can also help manage full-and part-time staff members.
Answer to Question 2
The server should get a parent's approval by inquiring if it is all right.