The Math Department has 6 committees that meet once a month. How many different meeting times must be used to guarantee that no one is scheduled to be at 2 meetings at the same time, if committees and their members are:
C1 = {Allen, Brooks, Marg}
C2 = {Brooks, Jones, Morton}
C3 = {Allen, Marg, Morton}
C4 = {Jones, Marg, Morton}
C5 = {Allen, Brooks}
C6 = {Brooks, Marg, Morton}