Instructions: This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Input: Passage: On November 30, 2010, CBC's senior director of regulatory affairs issued a letter to the CRTC regarding CBC's plans for transitioning to digital. The letter states, "CBC/Radio-Canada will not be converting its analogue retransmitters in mandatory markets to digital after August 31, 2011." On December 16, 2010, some months after the CRTC issued a bulletin reminding broadcasters that analog transmitters had to be shut off by the deadline in mandatory markets, the CBC revised the documents accompanying its August 6, 2010 news release to state that it had the money for and is striving to transition all 27 transmitters by August 31, 2011. Question: Why did the CTRC send out a bulletin to broadcasters?
Output:
reminding broadcasters that analog transmitters had to be shut off by the deadline in mandatory markets