Problem 4.13

A point \(A\) oscillates according to a certain harmonic law in the reference frame \(K^{\prime}\) which in its turn performs harmonic oscillations relative to the reference frame \(K .\) Both oscillations occur along the same direction. When the \(K^{\prime}\) frame oscillates at the frequency 20 or \(24 \mathrm{~Hz},\) the beat frequency of the point \(A\) in the \(K\) frame turns out to be equal to \(v\). At what frequency of oscillation of the frame \(K^{\prime}\) will the beat frequency of the point \(A\) become equal to \(2 v ?\)