a. One problem with the previous exercise is that it does not deal with the case when we "drop off the end" of the alphabet (or ASCII encodings). A true Caesar cipher does the shifting in a circular fashion where the next character after "z" is "a". Modify your solution to the previous problem to make it circular. You may assume that the input consists only of letters and spaces. b. Write a program that counts the number of words in a sentence entered by the user. c. Write a program that calculates the average word length in a sentence entered by the user.