please use SageMath 8.9 version to solve

Problem 5 Find several paragraphs of text written in English (eg from a book, magazine, news article, email exchange, etc). Strip out all non-letter characters (spaces, punctuation, numbers, etc), and convert all remaining letters to upper-case. Call this string CORPUS1. Ideally it should have at least 500 characters. Determine the relative frequency of each letter in CORPUS1. Your output should be a list of the frequencies of each of the 26 letters. Problem 5 Find several paragraphs of text written in English (eg from a book, magazine, news article, email exchange, etc). Strip out all non-letter characters (spaces, punctuation, numbers, etc), and convert all remaining letters to upper-case. Call this string CORPUS1. Ideally it should have at least 500 characters. Determine the relative frequency of each letter in CORPUS1. Your output should be a list of the frequencies of each of the 26 letters