Find length of time within range

I'm trying to understand length of an outage that occurs within time range.

In once cell I have the support period: Monday-Saturday 0800:18:00

In two other cells I have the start time and end time of the outage

Example: Outage Start: 13:00 Monday

Outage End: 19:00 Tuesday

Result should return: 15hours

Any advice appreciated!