A 140lb weight stretches a spring 20 feet. The weight hangs vertically from the spring and a damping force numerically equal to (7*sqrt(10))/2

times the instantaneous velocity acts on the system. The weight is released from 10 feet above the equilibrium position with a downward velocity of 42ft/s.

(a)	Determine the time (in seconds) at which the mass passes through the equilibrium position.

(b)	Find the time (in seconds) at which the mass attains its extreme displacement from the equilibrium position.