A diver can dive into a pool, descend, and ascend back to the surface very quickly. The depth of the diver can be determined with the equation h(t)=3t'2-12t+0, where h is the position of the diver, in feet, with respect to the surface of the water, and t is the time in seconds after the diver breaks the surface of the water.

Complete the square to determine how many seconds it will take the diver to return to the surface of the water.