Two Radio Antennas Are 120 M Apart on a North-South

Multiple Choice

Two radio antennas are 120 m apart on a north-south line,and they radiate in phase at a frequency of 3.4 MHz.All radio measurements are made far from the antennas.If the east-west reference line passes midway between the two antennas,what is the smallest angle from the antennas,measured north of east,at which constructive interference of two radio waves occurs? (c = 3.00 × 10⁸ m/s)

A) 43°
B) 22°
C) 68°
D) 47°
E) 30°