Exercise 4.6. Here we consider a vast generalization of edit distance, as follows. Suppose the cost of an edit sequence is given by a nonnegative real-valued function f(a,b,c) > 0, where a is the number of insertions, b is the number of deletions, and c is the number of substitutions. We assume that the function is monotonically increasing in each of its arguments. That is, increasing a, b, or c increases the value of f(a,b,c). Assume that f is provided as a subroutine that takes 0(1) time to evaluate. Consider the problem the minimum cost edit sequence w/r/t the cost function f. Show that either (a) computing a minimum f-cost edit sequence is as hard as SAT, or (b) design and analyze and efficient algorithm, as fast as possible, for the minimum f-cost edit sequence