First, we need the volume of the room. We get this by multiplying the length, width, and height. This gives us 18,000 ft^3. Now, we see how many BTUs were created. We do this by multiplying 2,200 by 20. This gives us 44,000. Now, we divide 44,000 by 18,000 to get our answer, which is 2.44 BTUs/ft^3, or C.