Submission of lecture 4 homework task mailroom madness

It's generally not a good idea to rebind a symbol used in `if...elif` conditional statements inside the body of any of the `if` or `elif` blocks. As doing so can produce unintentional side effects. I realize it's not possible in this particular case, but what would the user's experience be if `thank_you_prompt()` returned `u"2"`?

Also, you can just call the function without assigning the call to a symbol:

    thank_you_prompt()
    # vs
    reply = thank_you_prompt()