C.29.BB:4.2 - Identify transfers and internal production or removal

For each included part, distinguish the amount crossing into it, the amount crossing out, and the change created or removed within it under the chosen quantity definition.

Orient each transfer once. When a transfer from part i to part j removes amount f from i and adds the same amount to j over the common interval, use -f and +f in their accounts. If a connector stores some of the quantity, its incoming and outgoing amounts can differ; represent that store or retain both crossings.

Production and removal depend on the quantity. A reaction can change the amount of one chemical species within a vessel. Completing a job removes it from the population of unfinished jobs. Determine those terms from the relevant physical or counting rule. Assign each contribution once: classify completion as a crossing out of the population or as removal under its counting rule, and use that convention throughout.

Do not set an unobserved term to zero merely because the first diagram omitted it. Use a supplied law, a justified approximation, a bound, or an unresolved term according to what the answer needs.