a. Assume that the entire of relation R(A, B) fits in the available main memory but relation S(A, C) is too large to fit in the main memory. Find a fast join algorithm, i. e., an algorithm with the lowest number of I/O access, for the natural join of R and S. Justify that your proposed algorithm is the fastest possible join algorithm to compute the natural join of R and S. Next, assume that there is a clustered index on attribute A of relation S. Explain whether or how this will change your answer.