In the figure, a French submarine and a U.S. submarine move toward each other during maneuvers in motionless water in the North Atlantic. The French sub moves at speed vF = 46.00 km/h, and the U.S. sub at vUS = 69.00 km/h. The French sub sends out a sonar signal (sound wave in water) at 1.000 x 103 Hz. Sonar waves travel at 5470 km/h. What frequency is detected by the French sub in the signal reflected back to it by the U.S. sub?