An isolated system consists of a 1.5 kg mass moving in the presence of the following potential energy function: U open parentheses x close parentheses equals open parentheses 1 third straight J over straight m cubed close parentheses x cubed plus open parentheses 1 half straight J over straight m squared close parentheses x squared minus open parentheses 2 straight J over straight m close parentheses x What is the period (in s) of small amplitude oscillations of this system about its stable equilibrium point?