I'm not sure what your four step plan is, but here is how I would solve it:
50 rooms on each upper deck x 2 decks = 100 rooms
100 rooms x 1000 per room = 100,000
That leaves 48 rooms on the 2 lower decks, so 48/2=24 rooms per lower deck
48 rooms x 900 per room = 43,200
100,000 + 43,200 = $143,200 (maximum room sales amount)
Hope this helps!! :)