Answer: C

The question is: Is k > n ?

Statement (1) is insufficient. It tells us n = 2k - 200. If k is greater than 200, then n is greater. For instance, if k = 300, then n = 2(300) - 200 = 400. However, if k is smaller than 200, the opposite is true. If k = 150, then n = 2(150) - 200 = 100. We don't know the range of values for either k or n, so we can't answer the question.

Statement (2) is also insufficient. This doesn't tell us anything about the relationship between the donations, or about Nell's amount.

Taken together, the statements are sufficient. Since we know k is greater than 250, it must be greater than 200, meaning that Nell's contribution was greater, according to the equation in (1). Choice (C) is correct.