Two loudspeakers are driven in phase by an audio amplifier at a frequency of 600 Hz. The speakers are on the y axis, one at y = + 1.00 m and the other at y = -1.00 m. A listener begins at y = 0 a very large distance D away and walks along a line parallel to the y axis. (See Problem 20)

(a) At what angle θ will she first hear a minimum in the sound intensity?

(b) At what angle will she first hear a maximum (after θ = 0)?

(c) How many maxima can she possibly hear if she keeps walking in the same direction?