I try but error always appears, would you help me solve by using Sagemath(python), thank you.

Problem 4 I made a string of capital letters by starting with some lyrics of a song written in English and stripping out all spaces and punctuation. I then encrypted this string with the shift (Caesar) cipher, obtaining the string below. What string did I start with, and what key did I use? EVMVIKYFLXYKZUSVFERSFRKZKURSZXSCLVNRKVIPIFRUGFJVZUFECFFBRKDVEVMVIKYFLXYKZUJVVKYVURPNYVERSZXSFRKTFDZEXDPNRP 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