How many different ways can 2 students be seated in a row of 8 desks, so that there is always at least one empty desk between the students?  Choose the correct answer
A) 50
B) 42
C) 24
D) 20
E) 12

Rationale: "21 ways to seat the students : with two empty seats between 1 empty w / one student on the left most 1 empty . . . . right most two students can be interchanged 21 x 2 = 42 b"
Answer: B