Christopher is going to install wallpaper on the four walls of his room. two of the walls are 14 feet long by 9 feet high. the other two walls are 20 feet long by 9 feet high. his options at the wallpaper store are below.

one single roll of wallpaper costs $20 and covers 18 square feet of area.

one double roll of wallpaper costs $40 and covers 54 square feet of area.

what is the minimum cost of installing the wallpaper on the four walls of christopher's room?