Please assist as soon as possible. 

A union business representative, Tim, received a phone call from his shop steward, Sam,  around 10am on Friday morning. Apparently, the area manager, Mark, assigned work traditionally performed by Sam's trade to two non-union general maintenance workers. (Six months earlier, a similar incident occurred within this school system and Mark assured Tim that misalignments of this trade's work would cease and desist. In fact, Mark requested that Tim forward a jurisdictional list so he could identify this type of work and avoid similar issues in the future.) Tim was able to contact Mark by noon and arrange for an on-sight meeting at 3pm that same day to discuss the potential grievance at hand. When the three met, Tim explained to Mark that the unloading and staging of finished materials have historically and traditionally been performed by his collective bargaining unit's craftspeople. Mark said that there was very little work performed by these two maintenance workers and therefore, no reason to be concerned. Sam expressed his concern that Mark had not fulfilled his promise from six months ago. Although the conversation remained civil, both Tim and Mark stood their ground. Briefly describe how you would help Tim resolve this matter utilizing an interest based bargaining strategy. 

Please assist as soon as possible.