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 unit that were combined to form the Royal Irish Regiment was established first? Passage:He was Commanding Officer of 1Bn Royal Irish Rangers from February 1989 to August 1991. He attended the Higher Command and Staff Course, graduating in April 1991, and was promoted to colonel on 30 June 1991. From August 1991 to January 1992, he was based in Northern Ireland, overseeing the amalgamation of the Ulster Defence Regiment and the Royal Irish Rangers into the Royal Irish Regiment. He was promoted to brigadier on 31 December 1991, with seniority from 30 June 1991. From January 1992 to November 1993, he was commanding officer of the 48 Gurkha Brigade in Hong Kong. He was posted to the Ministry of Defence from November 1993 until January 1997 as Director of Public Relations (Army).
b