Write a regular expression to denote the set of all strings of letters that contain the five vowels in order. Assume that letters can only be lower case. Then, re-state the regular expression in terms of a context free grammar. So to be clear, the vowels will only appear 1 time and in order, i. e. a will be before e, e will be before i, i will be before o, and o will be before u. The other letters may or may not appear at all and can be before, in between, or after the vowels.