We have a project which a bus line provides (15) trips on a Saturday and (11) trips on a Sunday, with an average of (13) trips between the (2) days.  The credit language states that an average may be used when the number of weekend trips differs per day.  Would the average of (13) be used for the entire weekend across the (2) days (Saturday and Sunday) or is it an average of (13) trips per day for each day of the weekend?