The New Gotham Department of Transit is taking an inventory of its vehicles. There are three times as many buses as train cars. 20 percent of the buses are powered by alternative fuels, of which 40 percent are powered by biofuels, 20 percent by hydrogen, and the remainder by natural gas. 25 percent of train cars are less than 5 years old, which is half the rate for natural gas buses. What percentage of New Gotham's vehicles are natural gas buses that are least 5 years old?
문제집에서 풀고 있는데 답도 안 써있어서 풀이를 모르겠습니다ㅠㅠ 중간에 which is half the rate for natural gas buses 가 해석이 잘 안 되는데 고수님들 혹시 설명해주실 수 있으실까요?? 감사합니다ㅠㅠ