An author of two publications and a journalist, but not a free-lance writer, wrote
afor me below. I don't believe it is grammatical, but given that his writing ability trumps mine, I thought it best I do a wee sanity check

He is discussing the relationship between a free-lance writer and a publishing company.
a. I'm not a free-lance writer for the paper, in which the paper might give a writer a set amount of money for a particular story.I have used different relative pronouns below as variations, the first of which I don't believe is correct, but the second of which may be the best of the three:
b. 'Im not a free-lance writer for the paper, as which the paper might give a writer a set amount of money for a particular story.c. I'm not a free-lance writer for the paper, where the paper might give a writer a set amount of money for a particular story.Which of these, if any, are grammatical?
If one or more are incorrect, why is this so?
Thanks