Please write a short essay, of about 500 words, explaining how you would build a system for filtering and routing your electronic mail. Assume you have a mail handling system that can do the mail related part of this, and all you need to do is develop a module that will take a mail message as input and produce as output a ranked list of names of folders in which this message should be filed. Your module should be knowledge-based, and so may work with rules like Information Lens. It should have some type of lexicon, to help solve the vocabulary problem. It should have some memory and reasoning component to help with message classification. Give as many details as you can about data structures and algorithms you would use.