Alice drops a watermelon from the observation deck of a building 100 m above the ground. Standing directly below the watermelon, Bob fires an arrow straight up at 80 m/s at the same time Alice drops the melon. (a) (10 points) At what height above the ground does the arrow strike the watermelon? (b) (4 points) What is the minimum speed the arrow must have in order to strike the watermelon while the arrow is moving up?