Consider the following manufacturing process flow diagram with $5$ resources $($each working on a distinct activity$).$ Processing times are provided within each of the boxes corresponding to activities.

Picture$1-1.$png

To improve the process capacity, we should add a resource to step

B

$.$ As a result of this change, if that resource is no more the bottleneck, the process would be capable of satisfying a demand of

$[$ Select $]$

units per hour.