Two ships are moving along a line due east. The trailing vessel has a speed of 62.0 km/h relative to a land-based observation point, and the leading ship has a speed of 31.0 km/h relative to the same station. The trailing ship transmits a sonar signal at a frequency of 1200 Hz. What frequency is monitored by the leading ship? (Use 1520 m/s as the speed of sound in ocean water.) (Answer to the nearest 0.1 Hz.)