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Explanation

We would conjecture that if you see a GMAT question that
has a tank of liquid, there is about a 33% chance it's a geometry question, a
33% chance it's a solution question, a 33% chance it's a combined rate
question, and about a 1% chance that it's something else. This is a combined
rate question: all we have to know is the rate of water in and the rate of
water out. The net rate will be the difference between those two rates. On to
the data statements. Separately First. Statement (1) is irrelevant; insufficient.
Statement (2) gives us the two rates we need, so it is sufficient.

The correct answer is (B).

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