Length is not much of a factor in the evaluation, relevance is. These answers should be about 1/2 to 3/4ths of a page, excluding any diagrams you may include, where relevant.
Question 1. What are the problems with determining the value of a public good to society?
Question 2. Since economics seeks to bring about the efficient allocation of scarce resources, indicate clearly, which market is likely to bring about the greatest efficiency in allocation and why, compared to the other markets.