Here's my solution. After finishing this I reviewed the other solutions and my solution is a lot like one of the two that seemed to be the most common. The choices seemed to be to either do the distance calcs and then add the distance to the orders or join the stores to the orders and then do the distance calc.
I wasn't exactly sure what I was supposed to calculate, I mean the role of Required and Assigned fields in the second input. But looking at one solution solved that misunderstanding for me.