Physics problem on net force

[RHSLilSweetie07]

A circular hatch in the hull of a submarine has a radius of 40.0 cm (0.40 m). The submarine is 850.0 m under water. If atmospheric pressure above the ocean is 1.01*10^5 PA and the air pressure inside the submarine is 1.31*10^5 Pa, what net force is exerted on the hatch?

I have no clue how to work this problem. Please help me.

 

[Gene]

Your book should tell you what to use for the density of sea water in Newtons/m³.
P=height times density.
Add the air pressure to that and subtract the submarine air pressure.
If it is positive the force is inward, negative outward.
Multiply by the area of the hatch (m²) for the force.

 

[RHSLilSweetie07]

the density of sea water is 1025 kg/m^3.