JL.63 Swansong, a new cell phone manufacturer, wants to give customers more choice in the selection of back covers for their phones. Customers order the phones directly from the manufacturer and can select from the following materials for the back cover of the phone: bamboo, walnut, black aluminum, and plastic covers in a variety of colors. The bamboo back cover is particularly popular with daily demand being 33 units per hour. This cover is produced on site in the same line that produces the walnut cover. Lead time for the bamboo back cover is 11 hours and the kanban container size is 60. The manufacturer likes to keep a 16 percent buffer of safety stock on hand for the bamboo covers. Given the above information, how many kanbans do they require for the bamboo back cover? (Display your answer to the most appropriate whole number.)