With respect to large unions with a national presence, should prerogatives at the local or national level take higher priority when negotiating new agreements with employers? for example, if a new union were voted in to represent walmart employees, would it be better if the union negotiated one big nation-wide contract for all stores and all employees? or would it be better for the union to negotiate different terms at the individual store level (i. e. treating each store as a separate employer)? explain your reasoning.