A process consists of steps A$,$ B$,$ and C with capacities of $50$ units per hour, $40$ units per hour, and $60$ units per hour respectively. Which of the following statements is best?

A$.$ If step $A$ is improved so it can produce one unit per minute, the company has saved about $8$ minutes per hour.

B$.$ There should be a small amount of inventory in front of step $C.$

C$.$ There should be a small amount of inventory in front of step $B.$

D$.$ If demand is $50$ units per hour, the manager should try to balance capacity with demand so that steps A$,$ B$,$ and C each have a capacity of $50$ units per hour.