help! GWD 5-3

这道题没有找到解答。请教NN了。多谢！！！ Q3:

Material A costs $3 per kilogram, and material B costs $5 per 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.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

I chose E. why the key is B, please help me to solve it.

1、x+y=10 y>4并不能保证x>y

2、3x+5y<40 带入x+y=10 得到y<5 则必然有x>5 x>y 选B

1、x+y=10 y>4并不能保证x>y （如y=5, 则x＝y＝5；如y>5, 则y>x ； 所以不定）

答案还是B