Physics Wave Optics Level: Misc Level

A person driving at v=16.6 m/s crosses the line connecting two radio transmitters at right angles, as shown in the figure below.The transmitters emit identical signals in phase with each other, which the driver receives on the car radio. When the car is at point A, L1= 440 m and L2= 141 m away from the transmitters, the radio picks up a maximum net signal. What is the longest possible wavelength of the radio waves?