Section 18 The shared influence rule, functional version

What about when we combine maps according to the shared influence rule?

There is nothing to say because there is no problem; this way of joining maps together does not result in a new functional combination which needs calculating.

One might be tempted to think that “driving” both Q and E would somehow “exhaust” B. But if we needed to take into account some factors which would indeed affect the value of B, we would need a corresponding mini-map in which B was the consequence variable.