A university library has 12,000 registered members, divided into four membership categories:
| Category | Members |
|---|---|
| Undergraduate | 6,000 |
| Postgraduate | 3,600 |
| Staff | 1,800 |
| Alumni | 600 |
The library wants a proportional stratified random sample of 300 members, so that each category's share of the sample matches its share of the membership.
How many Staff members should be selected?
Select all that apply.