During Contract Negotiations the Union Negotiator Has Brought Up the Issue

During contract negotiations the union negotiator has brought up the issue of changing the way overtime work is scheduled.

A) Management does not need to negotiate on this issue because it is a permissive issue.
B) Management must negotiate on this issue as it is a mandatory issue.
C) This is a non-negotiable issue because scheduling is part of management's rights.
D) Because the union negotiators are asking for a higher level of overtime pay than time-and-a-half, this is an illegal issue and management may refuse to negotiate.