Please answer this: Extract the answer to the question from the following context. Question: What are types of copper minerals? Context: Copper is synthesized in massive stars and is present in the Earth's crust at a concentration of about 50 parts per million (ppm), where it occurs as native copper or in minerals such as the copper sulfides chalcopyrite and chalcocite, the copper carbonates azurite and malachite, and the copper(I) oxide mineral cuprite. The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal, with the largest described single crystal measuring 4.43.23.2 cm.
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Answer: the copper carbonates azurite and malachite, and the copper(I) oxide mineral cuprite

Please answer this: Extract the answer to the question from the following context. Question: Why was there originally a need for vacuum powered instuments on an aircraft? Context: Manifold vacuum can be used to drive accessories on automobiles. The best-known application is the vacuum servo, used to provide power assistance for the brakes. Obsolete applications include vacuum-driven windscreen wipers and Autovac fuel pumps. Some aircraft instruments (Attitude Indicator (AI) and the Heading Indicator (HI)) are typically vacuum-powered, as protection against loss of all (electrically powered) instruments, since early aircraft often did not have electrical systems, and since there are two readily available sources of vacuum on a moving aircraftthe engine and an external venturi. Vacuum induction melting uses electromagnetic induction within a vacuum.
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Answer: since early aircraft often did not have electrical systems

Please answer this: Extract the answer to the question from the following context. Question: What is the busiest train route in the country? Context: Union Station is further served by four Amtrak lines: the Northeast Regional and the high-speed Acela Express provide service to New York, Washington, D.C. and Boston, and rank as the first and second busiest routes in the country; the New HavenSpringfield Line provides service to Hartford and Springfield, Massachusetts; and the Vermonter provides service to both Washington, D.C., and Vermont, 15 miles (24 km) from the Canadian border. Amtrak also codeshares with United Airlines for travel to any airport serviced by United Airlines, via Newark Airport (EWR) originating from or terminating at Union Station, (IATA: ZVE).
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Answer:
Northeast Regional