Count average sales of distinct stores in excel

Hey team, I am having the darndest time figuring this one out. Any help would be greatly appreciated.

The question: What are average sales by week for the total # of stores by week? Create new functions to find average sales and number of stores for a pivot table without inserting a calculated field.

Pivot tables can give me the sum of sales and the distinct # of stores, but i want to create a range in my table to run a pivot off of to answer this question. I am using OLAP data so inserting a calculated field is not an option.

I've attached an example where I hard coded the data, but the goal is to have functions calculate columns F and G. Thank you in advance!

-Counting John

Ave_Sales_Weekly.xlsx

Is this some kind of homework?