听力原文：Japanese electronics maker Toshiba said Monday that it was buying nuclear plant builder Westinghouse Electric, the US-based unit of the British government's British Nuclear Fuels, for US ＄5.4 billion. Toshiba Chief Executive Atsutoshi Nishida said that while the price might seem quite high, Toshiba had a lot of competition for the company and that the future growth and profit potential of the business made it the correct price. By 2020 the market for nuclear power generation is expected to grow 50 percent compared to 2005, Nishida said at a London news conference. 'Toshiba is responding to this challenge by acquiring Westinghouse.' Upon completion of the acquisition, Toshiba expects its nuclear power business to expand to three times the current level by 2015 as a result of operational and technological synergies, Toshiba said in a statement. Toshiba expects to close the deal within six months and is not expecting regulatory troubles, Nishida said.Westinghouse will keep its headquarters in Pennsylvania, as well as its equipment, employees and trademarks, he said. Toshiba, which makes electronic goods including DVD players, semiconductors, electric motors and power systems, is preparing for an expected surge of new investment in power plants in China, India and the US. Westinghouse, which has built most of the nuclear reactors in the United States, is likely to design the plant and service them when they come online. What does the passage mainly discuss?