CXD page184第七题 if a certain grove consists of 36 pecan tress, what was the yield per tree last year? (1)the yield per tree for the 18 trees in the northern half of the grove was 60 kilograms last year. (2)the yield per tree for the 18 trees in the eastern half of the grove was 55 kilograms last year. 这题为什么答案选E，我怎么觉得应该选C啊？不可以用（18×60＋18×55）/36求出吗？各位高手请帮我看看 | 
