GWD-12-33

What is the volume of the cube above?

(1)   The surface area of the cube is 600 square inches.

(2) The length of diagonal AB is 10√3 inches.

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.

答案是D，但是根据(1)得出ab＋ac＋bc=300,根据（2）得出a²+b²+c＝300，三个未知数要有三个方程才能解出啊，为什么答案不是E呢？请指教