The area of the classroom is 8,671 in squared. you get this by multiplying base x height x width. You plug the same formula into the dollars he mentions and get 0.06890922 in squared. Than you divide the classroom dimensions by the dollar dimentions. that's 8,671 รท 0.06890922 = 125,832.21809795. rounding that to one decimal place, it would take $125,832.2 to fill up the classroom. (I might have gotten this wrong but I think this is the answer)