A mass weighing 8 pounds is attached to a hanging spring and stretches it 4 feet before it reaches an equilibrium. The system is immersed in a medium that offers a damping force that is numerically equal to the instantaneous velocity. The mass is initially released from a point 1 foot below the equilibrium position with a upward velocity of 4 ft/s. Find x(t), the displacement of the object from the equilibrium position at time t. When does the mass pass through the equilibrium position for the first time?