Here's a worker's activity log. I am interested in adding up "minutes worked", but only minutes that do not overlap. In other words, multi-tasking is not rewarded, per se.
<tbody>
Task
Work started
Work ended
Minutes worked
Date
A
5:00PM
6:15PM
75
1/13/2017
A
2:00PM
4:00PM
120
1/15/2017...