excel, use pivot table to count activities by month and average by activity

I have 3 tables, person, activity and a log of activities, with a line for each person and activity.

table person:

person_id  name      age  gender
1          personA   25  M
2          personB   25  F

table activity:

activity_id  name       type
1            activityA  X
2            activityB  Y

table log:

date        hour   person_id activity_id month
2015-01-01  10:00  1         1           January
2015-01-01  10:00  2         1           January
2015-01-02  10:00  1         1           January
2015-01-02  10:00  2         1           January
2015-02-01  15:00  1         2           February

Using Excel 2013 and relationships I was able to count the number of persons by activity, month, gender, etc. But I cant get the average of persons by activity/month and the number of distinct activities by date.

Any ideas? Thanks