When a .22-caliber rifle is fired, the expanding gas from the burning gunpowder creates a pressure behind the bullet. This pressure causes the force that pushes the bullet through the barrel. Suppose the barrel has a length of 0.511 m and an opening whose radius is 2.55 x 10-3 m. A bullet (mass = 2.6 x 10-3 kg) has a speed of 433 m/s after passing through this barrel. Ignore friction and determine the average pressure of the expanding gas.