Write alternative implementations for the is Re () function in Section 3.9. For one alternative, instead of only checking whether the subject of a message begins Re:, look also for Fwd: Re:. For a second alternative, check for Re: anywhere in the subject, not just at the beginning of the string. Analyze the output from these 3 functions, including the original is Re () function in Section 3.9. How many more messages have a return value of TRUE for these alternatives, and are they all ham? Which do you think is most useful in predicting spam?