You have to make a string of length 7, using lowercase letters only. Here are some conditions on the strings: (i) The first letter can be any lowercase letter. (ii) A vowel must be followed by a consonant, and vice versa. (For example, if the first letter is a vowel, then the second one must be a consonant, and the third letter must be a vowel, and so on. Similarly evaluate the case of the first letter as a consonant.) (iii) A letter can be used as many times as possible. How many such strings are there?