Current Attempt in Progress

In the figure, two blocks $(m=1\mathrm{.}90kg$ and $M=10\mathrm{.}5kg)$ and a spring $(k=250\frac{N}{m})$ are arranged on a horizontal frictionless surface. The coefficient of static friction between the two blocks is $0\mathrm{.}370.$ What amplitude of simple harmonic motion of the spring$-$blocks system puts the smaller block on the verge of slipping over the larger block?

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