This figure shows the floorplan of a room that incluldes a door and a window that have a combined area of 50 ft^2. Each side of the room has a wall that is 10 feet tall, and adjacent walls meet at right angles. If a can of paint covers an area of 300 ft^2, hwo many whole cans of paint must be purchased to paint the interior walls of this room, not including the door and the window?