I would say 6 1/2 rooms or round it off to 7 to break even. For one month, the income per room would be $25x31=$775. Of this, 40% of this or $310 would be variable expenses per room. So per room, the net income would be $775-310=$465. For the fixed cost of $3000/465= 6.45 rooms call it 7 rooms.
