A mass of 3 kg stretches a spring 6 cm. The mass is acted on by an external force of 10 sin(t/4) N (newtons) and moves in a medium that imparts a viscous force of 12 N when the speed of the mass is 4 cm/s. If the mass is set in motion from its equilibrium position with an initial velocity of 7 cm/s, formulate the initial value problem describing the motion of the mass. Use g = 9.8 m/s2 for the acceleration due to gravity. Let u t measured positive downward, denote the displacement in meters of the mass from its equilibrium position at time t seconds.