(Solved): Employees of a firm recelve annual reviews. In a certain department, 4 employees received excellent ...

Employees of a firm recelve annual reviews. In a certain department, 4 employees received excellent ratings, 16 received good ratings, and 1 received a marginal rating. If 3 employees in this deportment are randomiy selected to complete a form for an internal study of the firm, find the probability that the following occurs. (Enter your probabilities as fractions.) (a) All 3 seiected were rated excellent. (b) One from each category was selected.