I need to replace light fixtures in an old large boiler room in an apartment building. The room is about 35' by 40' and 23' tall. I'm looking at led fixtures with options for 12,000, 18,000 and 24,000 lumens. These fixtures will be hung 20' above the floor. I have no idea how many lumens I need. The owner wants the room to be well lit. The room has a lot of pipes running around. The walls and ceiling will be painted white. Could anybody help me figure out which lumen output and how many fixtures I should install?