Terrence was filling the new fish aquariums where he works. He was able to fill 1 and one-third aquariums in 2 and one-half hours. At this rate, how long will it take him to fill 4 aquariums?

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).