Two in-phase loudspeakers, 15.0 m apart, are setup in an open field to avoid reflections from objects. Each speaker is producing 250 Hz tones and the speed of sound is 340 m/s. A person stands at the midpoint between the speakers. (a) What does this person hear, constructive or destructive interference? Why? (b) They now walk towards one of the speakers. How far from the center must they walk before they first hear the sound become a minimum intensity? (c) How far must they walk from the center before they first hear a sound intensity maxima? (d) Repeat (a) through (c) if the speakers are 180° out of phase.