The sound signal from the fall of a large block of ice from a glacier is detected by two devices located on a boat, with detector A immersed in water and B on the bow of the vessel. It is known that the speed of sound in water is $1540 \frac{\mathrm{~m}}{\mathrm{~s}}$ and in air is $340 \frac{\mathrm{~m}}{\mathrm{~s}}$.
The graphs indicate, in real time, the sound signal detected by the two devices, which were turned on simultaneously at an instant before the ice block fell. By comparing corresponding points of this signal in each device, it is possible to obtain information about the sound wave.
The distance L, in meters, between the boat and the glacier is closest to
(A) 339000.
(B) 78900.
(C) 14400.
(D) 5240.
(E) 100.