Given the task definition and input, reply with output. 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.

Question: Which of Sylvius' teachers at Leiden University taught there first? Passage:Sylvius, a latinization of "de le Boe" translated as "of the woods", was born in Hanau, Germany to an affluent family originally from Cambrai, but worked and died in the Netherlands. He studied medicine at the Protestant Academy of Sedan, and from 16321634 in Leiden under Adolph Vorstius and Otto Heurnius. In 1634 he held a disputation Positiones variae medicae under the presidency of Vorstius, in which he defended the proposition that there should be a pulmonary circulation. After that Sylvius made a study tour to Jena and Wittenberg, and on 16 March 1637 he defended a thesis entitled De animali motu ejusque laesionibus at the University of Basel under the presidency of Emmanuel Stupanus. After practicing medicine in his hometown Hanau he returned to Leiden in 1639 to lecture. In this period he became famous for his demonstrations on circulation. From 1641 on he had a lucrative medical practice in Amsterdam. While in Amsterdam he met Glauber, who introduced him to chemistry. In 1658 he was appointed the professor of medicine at the University of Leiden and was paid 1800 guilders which was twice the usual salary. He was the University's Vice-Chancellor in 1669-70.
b