Final answer:
The choice of a classmate as a study partner would rely on how their grading happiness aligns with one's own academic goals, and the mutual benefit derived from the partnership. Preferences for grades and compatibility of motivations are crucial in this decision.
Step-by-step explanation:
The question centers on a hypothetical situation involving student partners with different levels of happiness derived from academic grades. If one classmate gets 50 units of happiness for a 'B' and 80 units of happiness for an 'A', while your preference remains the same, the efficacy of the partnership would depend on your own preference for grades and happiness. In deciding who you would prefer as a partner, you would have to consider the compatibility of both partners' goals and the motivation this partnership would provide towards achieving high grades.
On the subject of which classmate one would prefer as a partner, that choice would be contingent upon how each classmate's grading happiness aligns with your own goals and desire for academic success. Should your priorities align, it's feasible to assume that the classmate in question would also favor the partnership, presuming it furthers their interests in attaining high grades and the resultant happiness.