Afew weeks ago, frank you move to a new apartment, carrying heavy boxes up several flights of stairs with only a few good-natured complaints. this weekend, frank asks you if you would be willing to him out with repainting his apartment. frank is most likely hoping that will foster your willingness to do so

Reciprocity

Explanation:

Because of his help, which is not a small one since he has carried heavy things upstairs, he is hoping that reciprocity will make you willing to help him too.

This is referring to an obligation in returning the favor because he was doing that favor to you at first.

Then, both of you will have done a benefit that is good for both and this is considering a good action. He knows that you should be willing to do that more than anyone else because he has done favor to you.