做了第二遍，还是错了。。。答案为C ,我选D，请高手指点

The total cost of an office dinner was shared equally by k of the n employees who attended the dinner. What was the total cost of the dinner?

(1) Each of the k employees who shared the cost of the dinner paid $19.

(2) If the total cost of the dinner had been shared equally by k + 1 of the n employees who attended the dinner, each of the k + 1 employees would have paid $18.

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.

由（1）知total cost＝19k，可是并不知道k，所以没法求出

由（2）知 19k＝18（k+1)可求出k

故选C

我以为题目里面写了K，就代表K是已知数，所以我也选了D，嘻。

是不是GMAT里面的题目的结果都是不能含字母的？