A department runs exactly four classes, with 10, 20, 30 and 40 students enrolled. Every student is in exactly one class, so 100 students in total.
The registrar computes the average class size by averaging the four numbers.
A journalist instead picks one student uniformly at random from the 100 and asks how many students are in that student's class. Let be the number the student reports.
What is ?
Select all that apply.