Excel working out a formula for a 7 hour working day and average

Hi,

I have an query I need answering:

There is queries that are raised at work through a platform, when we download the data we split it into time created and time it was resolved.

I want to work out the time it took between creation and being resolved. However this is the problem -

How do I work out the resolution time for a 7 hour day format, i.e if a query is raised a 4:30pm on a Thursday and resolved at 10:00am on a Friday the resolution time (based on working 9-5) should be: 0 days 1 hour 30 mins 0 seconds or 00:01:30:00.

I need this for a large spreadsheet, I also have the queries split into categories and want to work out average time it takes to resolve a query per category.

If you could help this would be great!!!

This is an example of the data i work with

Created Resolved
02/04/2018 08:17 03/04/2018 09:05
03/04/2018 08:13 03/04/2018 09:15
03/04/2018 09:21 06/04/2018 09:09
03/04/2018 13:20 04/04/2018 09:53
03/04/2018 14:24 11/04/2018 16:29
03/04/2018 15:45 03/04/2018 15:49
04/04/2018 01:49 04/04/2018 07:52
04/04/2018 08:12 04/04/2018 09:44
04/04/2018 08:36 04/04/2018 09:07


Thanks,

Sam