######################Problem 3###########################
def sort_letters_backward(word):
    """prec: word is a lower-case string
    postc: returns a string with the letters in word sorted in reverse 
    alphabetical order
    """
    chars = list(word)
    chars.sort(reverse=True)
    return "".join(chars)
def sort_letters_backward(word):
    """prec: word is a lower-case string
    postc: returns a string with the letters in word sorted in reverse 
    alphabetical order
    """
    return "".join(reversed(sorted(word)))
def sort_letters_backward(word):
    """prec: word is a lower-case string
    postc: returns a string with the letters in word sorted in reverse 
    alphabetical order
    """
    return "".join(sorted(word, reverse=True))
def main():
    print("*************** Problem 3 Tests **************")
    print(sort_letters_backward("hammer") == "rmmhea")
main()