...additional time will it take? Here's the full question: A boat is floating at rest in dense fog near a large cliff. The captain sounds a horn at water level and the sound travels through the salt water and the air (340 m/s) simultaneously. The echo in the water takes 0.40 s to return. How much additional time will it take the echo in the air to return?

This is my attempt:

First I find the distance by using the ?d = V(?t) and then divide the distance by 2 since it takes twice the distance for the echo to come back, so I have a distance of 65M. Then I would this distance and the given velocity of the sound-wave to find the time it takes to reach where the sound bounces back and have a value ?t = 0.20 seconds. Then I add both, to get a total value of ?t = 0.60 seconds. Is this the answer? Or am I wrong?