The B&B Painting Co. is bidding on a job to paint the inside of an apartment building that has 4 units. Each unit is an

efficiency apartment in the shape of a rectangular

solid with a

length of 20 feet and a width of 30 feet. The ceilings are 9 feet tall. Assuming that they do not have to paint the floor or ceiling, how many

square feet of wall

space is there that needs to be painted?