Roberto has been a hard-working and high-performing distribution specialist for a food distribution company. Based on his good performance and positive interpersonal skills, he is appointed as team leader of the group that distributes food to schools and hospitals. Several weeks into the job, Roberto notices that the team of workers is really not working much like a team. The team members each seem to do their own job acceptably, but there is not a high level of cooperation and coordination among them. Roberto has been somewhat successful in his preliminary attempt to move the group toward better teamwork. To help sustain the teamwork, Roberto is advised to use which approach to leadership