The output from an assembly line is 1,600 units in an 8-hour shift. The item is moved in containers, each of which holds 50 units. Each container spends an average of 30 minutes in the production part of a cycle, and 20 minutes in the demand part. How many kanbans should be used for the item? What is the stock of work in progress? A scheme has been proposed to reduce the time in the demand part of the cycle to 15 minutes. How many kanbans should be used now? What is the margin of safety in each case?