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 the tributary of the Amazon that Crevaux descended to? Passage:The interior of French Guiana was virtually unknown and Crevaux decided to lead an exploration into its depths. On July 8, 1877 Crevaux traveled up the Maroni River where he encountered the Galibi and the Bonis. He left the Maroni to follow a tributary, the Itany River, along the way he visited the Roucouyenne and then followed an Emerillon trail over the spine of the Tumuk Humak Mountains. He descended the other side of the mountains to the Jari River, a tributary of the Amazon. By December 1877 he had reached the Brazilian city of Belém. He was nearly naked and had lost or used most of his possessions, and was believed by the Brazilian inhabitants to be an escaped French prisoner and was refused any help. He was eventually aided by a fellow Frenchman who bought him passage on a ship back to France. Upon returning to France, Crevaux gave an account of his journey to the Société de Géographie and was made a "Knight" of the Légion d'honneur.


a