JEE Main 2019 Physics question

A submarine (A) travelling at 18 km/hr is being chased along the line of its velocity by another submarine (B) travelling at 27 km/hr. B sends a sonar signal of 500 Hz to detect A and receives a reflected sound of frequency ν. The value of ν is close to: (Speed of sound in water = 1500 ms)

• (A)507 Hz
• (B)504 Hz
• (C)499 Hz
• (D)502 HzCorrect