I'm fairly aware that who is used for subjects and that whom is used for objects. However, what about when the object is actually being modified by a clause? I have the sentence
We can determine this by solving for the location of a consumer, ______ is indifferent to each of these stores.
Would who or whom be more appropriate in the blank? Would it be who because the customer is indifferent, or would it be whom, since it is the location of a customer?