Answer:
3 hours working on problems, 1 hour reading
Explanation:
From the given information:
We learned that If Nick can attempt more than 15 problems in an hour, working on problems will helo and aid further his grade for that particular hour than reading would.
We know that the marginal gain for three hours is greater than 15. This implies that Nick would get better by spending 3 hours on problem-solving and the rest 1 hour on reading since the marginal gain for that an hour is one problem solved. Hence, it will be advisable to spend it on reading.