A 80.0-kg airplane pilot pulls out of a dive by following, at constant speed, the arc of a circle whose radius is 300 m. At the bottom of the circle, where his speed is 180 km/h, (a) what are the direction and magnitude of his acceleration? (b) What is the net force acting on him at the bottom of the circle? (c) What is the force exerted on the pilot by the airplane seat?