Multiple Values for a cell

I am working on a spreadsheet that has three columns.

A - Product (stays the same no changes)
B - Amount Ordered (varies)
C - Purchased By (varies)

My goal is to set up a formula that shows a summary of how much a person has ordered. Sounds straight forward, but the problem I am running into is when 2 or more people are making a combined purchase. In those cases the cost will be divided equally between the buyers. Is there a way to achieve this goal?

I included a sample of the spreadsheet. Typically this is about a 300-400 line report.

Thank you.