SumIf using 2 criteria??

I have been having difficulty figuring out a way finding the sum of QTY (M) using 2 different criteria. One using company name (column A) and prouduct serial number (column I).

I have no problem simply finding the QTY of a specific product (using serial #) through sumif, but havent figured how to do it by doing customer and product serial at the same time.

Is there a way to use the sumif function for 2 seperate criteria? One is text...one is a serial code (all numbers)??

Thank you.