G7. how many strings of eight upper case english letters are there a) if letters can be repeated? b) if no letter can be repeated? c) that start with x, if letters can be repeated? d) that start with x, if no letters can be repeated? e) that start and end with x, if letters can be repeated? f) that start with letters bo(in that order), if letters can be repeated? g) that start or end with letters bo(in that order) if letters can be repeated?