$6.$ Krafty City is a large retailer that sells power tools and other hardware supplies. One of its products is the KraftyMan workbench. Information on the workbench is as follows: Annual Demand $=1,200$ Holding cost $=$ $$15$ per year Ordering cost $=$ $$200$ per order a$)$ What is the economic order quantity for the workbench? b$)$ Suppose that KraftyCity has to pay $$50$ per workbench for orders under $200,$ but only $$42$ per workbench for orders of $201$ or more. What order quantity should KraftyCity use? a$)$ Is there any difference between the optimal annual cost between $($a$)$ and $($b$)?$ If so$,$ what is the percent difference?