In the figure provided, two boxes oscillate on a frictionless surface. The coefficient of static friction between the two boxes is 0.700 and the spring constant in the spring is 51.0 N/m. If the smaller box has a mass of 3.81 kg and the larger box has a mass of 7.42 kg, what is the maximum oscillation amplitude for which the 3.81 kg box does not slip?

Fig: 1

Fig: 2