Bobby can paint a certain fence in two hours, Zane Zachary can paint the same fence in three hours and Slow Sammy can) t the fence in six hours. If all three boys worked together, how long would it take them to paint the fence?

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).