Two identical loudspeakers are placed on a wall $2\mathrm{.}0$ m apart. A listener stands $3\mathrm{.}0$ m from the wall

directly in front of one of the speakers. A single oscillator is driving the speakers at a frequency of $300$

Hz$.$

a$.$ What is the phase difference in radians between the waves form the speakers when they reach the

observer?

b$.$ What is the frequency closest to $300$ Hz to which the oscillator may be adjusted such that the

observer hears minimal sound?