A company is using Kanban containers. There are two adjacent work centers, a downstream $($using$)$ and an upstream $($producing$)$ one. The using work center has a production rate of $200$ parts per day and each container holds $20$ parts. It takes $\mathrm{.}5$ days for a container to make the entire cycle from the time it leaves the upstream center until it is returned, filled with production, and leaves again. The manager wants a safety factor $($a$)$ of $20\%.$ The company is interested in reducing the number of containers.