Definition: In this task, you're given a question, along with a context passage. The passage will not have a direct answer to the question, but can include some information and a clue for the answer. Assuming you can only obtain information about one entity in the passage, your job is to determine whether information from the passage can be used to answer the question. Indicate your choice as `a` for Yes or `b` for No.
Input: Question: How long was Dariush Mostafavi the CEO at Persepolis? Passage:Mohammad Parvin began his career at the Persepolis youth academy in Tehran before signing his first pro contract in 2005. Despite the fact that his father was the head coach of the team, he remained unused until making his debut in a friendly match against German giants Bayern Munich. Being dubbed as a future star player in the national team, his time at Persepolis turned difficult following his fathers departure as a coach. He later followed his Parvin senior, who had become technical director of Steel Azin, and became the top scorer in the first division. Following a remarkable season in a star-studded second tier side, he chose to move soon, again shortly after his fathers resignation. Despite reportedly being offered a contract by Persepolis, he moved to Saipa. It was speculated that the reason for his refusal to play at Persepolis was the troublesome relationship between Dariush Mostafavi (then Club CEO at Persepolis) and his father Ali Parvin. After only 12 performances at Saipa, he spent 6 successful months on loan at Dunajská Streda in Europe only to return to his beloved Persepolis in July 2009. His second stint at the continents most popular football team, was another difficult experience and Mohammad was on the move once again in 2011. His next stop was Paykan, another short term stint as soon newly promoted Gahar Zagros followed.


a