Detailed Instructions: In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.
Problem:Question: From which companies did Amtrack purchase passenger rail service across the U.S. in 1971? Passage:Following its takeover of most passenger rail service in the United States on May 1, 1971, Amtrak retained the Abraham Lincoln as a daily Chicago-St. Louis service, operating in tandem with the GM&O's old Limited. In November of that year Amtrak extended both the Abraham Lincoln and the Limited (now known as the Prairie State) through Chicago to Milwaukee, Wisconsin. In October 1973, Amtrak replaced the rolling stock with the new French-built Turboliner; as part of this change the trains were re-branded as Turboliners and truncated to Chicago. In February 1976 Amtrak returned conventional rolling stock to the route and revived the Abraham Lincoln name along with the Ann Rutledge. Amtrak added the State House to the Chicago-St. Louis corridor in 1977. Also in 1977, Amtrak extended the Abraham Lincoln to Kansas City and renamed it the Ann Rutledgea name that had briefly disappeared from the timetable in 1976-77 when Amtrak extended the Inter-American to Chicago. Today service between Chicago and St. Louis is handled by the "Lincoln Service".

Solution:
Following its takeover of most passenger rail service in the United States on May 1, 1971, Amtrak retained the Abraham Lincoln as a daily Chicago-St