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Seven years ago,back in 2010,some reports covered a story that the world's longest railway tunnel was under construction in Switzerland.At that point it had already been under construction for over a decade.It had been voted to be built nearly a quarter of a century ago!The idea to build it could date back to nearly 70 years ago—about as old as some of your grandparents!
Yesterday,it was finally ready!
It's 35 miles long and runs 7,500 feet beneath the Swiss Alps,a famous mountain range in Switzerland.It even runs under an old tunnel that was there before.It took a total of 17 years to build at a cost of $12 billion.128 million tons of rock were dug.Two million truckloads of earth were removed!
The tunnel connects northern and southern Europe.The opening of this runnel was such a big deal that the Germany's leader,Chancellor Angela Merkel,France's president,Francois Hollande,and Italy's prime minister,Matteo Renzi,were an there to celebrate,as was Austria's chancellor Christian Kern.
It's called the Gotthard Base Tunnel.Eventually,325 freight and passenger trains will go through the tunnel,relieving a lot of traffic on the roadways there and making it a more environmentally friendly option.The Gotthard Base Tunnel is a wonder of engineering!Make us want to visit it!
（A，C为常数）．已知工人组装第4件产品用时30分钟，组装第A件产品用时15分钟，那么C和A的值分别是（ ）