A 4-person grievance committee is to be selected out of 2 departments, A and B, with 18 and 23 people, respectively. In how many ways can the following committees to selected?
a. 3 from A and 1 from B.
b. 2 from A and 2 from B.
c. All from A.
d. 4 people regardless of department.
e. At least 3 from department A.