instruction:
In this task, you're given a context, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both context and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the context or linked information.
question:
Context: the group originally included lead vocalist Keith Relf Link Information: The Yardbirds are an English blues rock band from London. Formed in May 1963, the group originally included lead vocalist Keith Relf Answer: Robert Plant
answer:
Which person was the lead singer of the Yardbirds the longest?


question:
Context: Blackpool Panthers were formed in 2004 and played in Co-operative Championship One. Link Information: The Rugby League Championships (known as the National Leagues between 2003-2008) are the two professional divisions below the Super League, consisting of 12 teams in the Championship and 14 teams in League 1. Answer: 14 teams
answer:
How many teams were in the league that the Panthers played in in 2004?


question:
Context: He sang frequently with the Boston Symphony Orchestra under conductor Charles Munch Link Information: 

In 1920, Munch became professor of violin Answer: 920
answer:

When did the conductor that McCollum sang under with the Boston Symphony Orchestra begin his career?