A 3.0 kg mass is attached to a spring. The mass is displaced from its equilibrium position by a distance of A=0.15 m. Assume friction is negligible. Show your work so that I can easily follow your reasoning. a. If it takes 0.50 seconds for the mass to return to its equilibrium position, what is the spring constant of the spring? (5 points) b. What is the mass' speed when it returns to the equilibrium position? (2 points)