4. The position of the block of a spring-mass system is given by x = 0.01 cos(wt). (a) If the spring constant and the angular frequency are 1200 N/m and 20 rad/s respectively, find the mass of the block. (b) Find the position, the velocity, and the acceleration of the block when t = T/4. (c) Find the kinetic energy of the mass and the potential energy of the spring when t = T/4