Consider modeling a warehouse with three in-flow arcs and three outflow arcs.  The warehouse node is a transshipment node but has a capacity of 100.  How would one modify the network model to enforce the capacity limit?

a. It cannot be accomplished; the problem now has to be modeled as linear program.

b. Separate the warehouse node into two nodes, connected by a single arc, with capacity of 100.

c. Place a limit of 34 on each in-flow arc.

d. Add a side constraint limiting the out-flow arcs sum to 100.