Two train whistles, A

and B

$,$ each have a frequency of $392$ Hz

$.$ A

is stationary and B

is moving toward the right $($away from A

$)$ at a speed of $35\mathrm{.}0$ m$/$s

$.$ A listener is between the two whistles and is moving toward the right with a speed of $15\mathrm{.}0$ m$/$s

$($Figure $1).$ No wind is blowing. Take the speed of sound to be $344$ m$/$s

$.$

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