In the figure on the left (above), the spring pulls the mass toward the shaft with a force of 12.0 N. What is the mass M? (Ignore the weight of the pan on which the mass is sitting. The pulley and string are both massless, and the pulley is frictionless) Assume the acceleration due to gravity is 9.81 m/s^2 and write your answer in kg. present answer with with 2 significant figures