Okay so i am not completely sure but when i looked at it , i feel like you have to figure out how much each square foot will cost so divide 180,000 by 45,000 since that will be the total in the end. each one will cost 4 dollars each one so then do 4800 times by 4 which equals 19,200 and then 9200 times by 4 equals 36,800. please get back to me whether this answer was right or not ? glad to at least be able to try and help !