9. A seagull, flying above a lake, dives for a fish according to the function h(t)=0.25t3-4t2 +15t, where h(t) represents the height above the water, in feet, at t seconds. a) Determine the velocity of the seagull when it exits the water, (with the fish in its mouth). (Round to 2 decimal places.) b) Determine the acceleration of the seagull at 9 seconds. (Round to 2 decimal places.)