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Solutions to \href{Problem \href{http://isites.harvard.edu/icb/icb.do?keyword=k91266&pageid=icb.page545995}{Problem  Set 2}{http://isites.harvard.edu/icb/icb.do?keyword=k91266&pageid=icb.page545995} 2}  of Harvard's AY 201b course (2013).