In fog, a lightship warns nearby ships by sounding a horn in the air and striking a bell under the water at the same instant. A ship 1020 m from the lightship detects the bell with an underwater microphone and the horn with a microphone on its deck.
The speed of sound is 340 m/s in air and 1500 m/s in seawater.
Calculate the time interval between the ship detecting the bell and detecting the horn.