A swimming pool holds 540,000 L of water the pool has two drainage pipes. When the pool is completely full, the first pipe alone can empty it in 180 minutes, and the second pipe alone can empty it in 120 minutes. When both pipes are draining together, how long does it take them to empty the pool?

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).