Transients for complex occupancy

In trying to determine the peak transients and daily average transients for a building with several distinct user groups, my client has given me a schedule of when each group will use the building and a range in the number of people (e.g., 6:00am-12:00pm: 100-150; 3;00pm-6:00pm:25-50). It also varies over the course of the year. I can use the higher number for the largest group for my peak transients. In figuring the average daily transients, I know that I'll have to weight each group by the number of days per year that they use the building. Should I use the higher number, or the mean of the range for each group?