New addition: the number of lines capacity to add to the plant

Construction takes 2 quarters.  This is an addition to the building in which new lines may be installed.  Only one new 2-line addition may be started in any quarter, but another could be started the following quarter so that two additions are under construction at the same time.  New lines must be installed separately during the last quarter of construction (or later).

Limits:  0 or 2 (to a maximum capacity of 12 lines)