Ten students have been nominated for the positions of secretary, treasurer, social convenor, and fundraising chair. In how many ways can these positions be filled if the Norman twins are running and plan to switch positions on occasion for fun since no one can tell them apart?

Answer: 4032

My answer: 4050

What I did was:

[10!/(2!(10-2)!] x [10!/(10-2)!] = 4050

Considering that the 2 twins are identical objects. Doesn't work. For some reason the book took the value as if all 10 were different individuals: 5040 and did times 0.8 to give 4032.

I can't figure this out...why time 0.8 wtf is going on

Thank you for help guys!!!!!