Table: tv_episode_16
Columns: episode
prod
title
directed_by
written_by
originalairdate
filmed

Question: How many episodes have the title "a perfect crime"?
SQL: SELECT COUNT("episode") FROM tv_episode_16 WHERE "title" = '"A Perfect Crime"'

Question: Who directed the epsiode with production number 109?
SQL: SELECT "directed_by" FROM tv_episode_16 WHERE "prod" = 109