Please answer this question

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 = 188 km/h, and the U.S. sub at Vus = 268 km/h. The French sub sends out a sonar signal (sound wave in water) at 1,103 Hz. Assume that sonar waves travel at 5000 km/h. Freach 1217:31 U.S. What frequency is detected by the French sub in the signal reflected back to it by the U.S. sub? Express your answer in Hz