Okay, I need some help yet again. Our teacher is giving us no hints on the "mystery problem" on our test tomorrow. "A boat sends a sonar down to find a submarine underwater. The boat estimates the velocity of sound under the water to be 1500 m/s. Howeer, they are wrong about that velocity. Find their mistake, explain it, and then find how deep the submarine is in the water and find the real velocity of sound under the water."