Permutation with repetition or conditions help please :)

In a railway car, 3 seats facing the engine, 3 seats with their back to the engine

engine
_|||||||||||||||||_
＝　＝　＝
＝　＝　＝
------------------

In how many ways can 6 people be seated if two of these people insist on facing the engine?

please help me :) thanks

first fill the "back to the engine" group in 4P3 ways from willing passengers
then seat "facing the engine" group in 3P3 ways
4P3*3P3 = 4*3*2*3! = 144 <---------