87. 從1961年以來，西方國家的農人平均每個人生產的糧食約多了四分之一，生產的成本則比以前降低了百分之四十。 Since 1961, farmers in the West have produced nearly _______________ food per person, and they have produced it at a cost _______________ than before. (答案中的百分比不得用符號表示)