formula to calculate average number workdays in queue

In the attached spreadsheet under the Stats tab I have D4 displaying how many jobs have been closed for the month of Nov.
I would like to populate E5 with the average number of days that it took to close the jobs.
If you notice in D4 limits the search to November and it's also looking for a code "P/S"
I'm looking at jobs coded "P/S" for November, the number of workdays in queue can be found in column N under Archive tab.
Can you help me with a formula that will give me the average workdays in queue for "p/S" jobs in Nov and put that formula in E5?

Thanks