Top spending users
Question
Suppose you have the following dataset which contains which contains (1st tab) a list of items purchased by a given user, (2nd tab) a mapping which maps the item_id to the item name and price, and (3rd tab) a matrix that formats data from sheet 1 into a matrix with users in rows and the number of each item_id purchased.
Given these 3 data sets, can you create a list of users who have spent the most?