1.material A cost $3/kilogram,material B costs $ 5/kilogram ,If 10 kilograms of material K consists of x kilograms of material A and y kilograms of material B ,is x> y ?
(1)y > 4
(2)the cost of the 10 kilograms of material k is less than $ 40
key：B 但我觉得 B 没办法判断啊 请教NN | 
