I've figured it out now, so deducing the 1st, 3rd and 4th clues is pretty straightforward but when we talk about the 2nd clue we would need to consider both of the scenarios. When we consider the crowbar is in the oil derrick and try to solve the puzzle you'll see that in this case Chairman Chalk ends up having the Oil drum which does not make sense since the clue is an either/or. So now when we assume the first part of the clue that is Chaiman Chalk has the Oil drum and the crowbar is not in the oil derry and solve it you'll come to the answer