Consider all the applicants as being three groups, one being business, another education and last recreation.

What you first need to see is that there is B, E and R groups (for the three groups)

How can they be arranged? (A)

Now, consider only the B group, there are 3 applicants. In how many ways can they be interviewed? (B)

Consider only the E group, there are 2 applicants. In how many ways can they be interviewed? (C)

Similarly, consider only the R group, there are 1 applicants. In how many ways can him/her be interviewed? (D)

The anwer will be the product of A, B, C and D.

Is that okay?