Custom column based on data before summary

I have the example data below:
POS.Scan Date is the date the product was scanned at the point-of-sale (sold date).

Seller.Name Brand.Name Model.Name Production.Serial Number POS.Scan Date
Wylie Acme Widget aw0001 1/1/2021
Wylie Acme Widget aw0002 1/1/2021
Wylie Acme Anvil aa0001
Wylie Acme TNT at0001 1/5/2021
Sam Acme Widget aw0003
Wylie Moxy Widget mw0001 1/3/2021

I want to filter and summarize the data as follows:
Seller.Name = Wylie
Brand.Name = *
Model.Name = *
count_rows(POS.Scan Date = not empty)
count_rows(Production.Serial Number)

The desired result:

Seller.Name Brand.Name Model.Name How many sold How many Produced
Wylie Acme Widget 2 3
Wylie Moxy Widget 1 1
  1. How do I create the custom “How many sold” and “How many Produced” columns?
  2. How do I create a base question that allows other users to modify the Seller.Name, Brand.Name, Model.Name filter parameters and have the sold/produced columns automatically calculated?