Please help me. 10 points to the first right answerer! :)?

A circular hatch in the hull of a submarine has a radius of 40.0 cm. The submarine is 850.0 m under water. If atmospheric pressure above the ocean is 1.01 X 10^5 Pa and the air pressure inside the submarine is 1.31 X 10^5 Pa, what net force is exerted on the hatch? (weird symbol that looks like a 'p' SW = 1025 kg/m )