A ball is dropped from a boat so that it strikes the surface of a lake with a speed of 16.5 ft/s. While in the water the ball experiences an acceleration of a=10-0.8v, where a and v are expressed in ft/s² and ft/s, respectively. Knowing the ball takes 3 s to reach the bottom of the lake, determine a.) The depth of the lake b.) The speed of the ball when it hits the bottom of the lake.