Problem 4: (25 pts) Consider the problem of counting, in a given text, the number of substrings that start with an A and end with a B. For example, there are four such substrings in AACBB. Design an algorithm for this problem and determines its efficiency. (5 bonus points: your algorithm should run in O(n) in the worst case.) Answer: Problem 4: (25 pts) Consider the problem of counting, in a given text, the number of substrings that start with an A and end with a B. For example, there are four such substrings in AACBB. Design an algorithm for this problem and determines its efficiency. (5 bonus points: your algorithm should run in O(n) in the worst case.)