A 4-letter code is to be formed using only letters of the alphabet, according to the following rules. (Note: There are 26 letters in the alphabet.)
Rule 1: If the code starts with a vowel (i.e., any of a, e, i, o or u), then it must end in y. (For instance, the code abcy could be formed.)
Rule 2: If the code does not start with a vowel, then there must be 2 consecutive positions in the code which contain the same vowel. (For instance, both baal and blaa are acceptable codes.)
There are no other restrictions. How many di?erent codes can be formed?