The pressure acting on a surface is defined as the ratio of force acting on the surface and the total surface area. In other words, pressure can be written as:
Pressure = force / area
this equation can be rearranged to determine force as a product of pressure and surface area. That is,
Force = pressure x area
Here, the total pressure acting on the given surface is 80 N/m^2 and the surface area is 5 m^2. Therefore, we can use the above equation to calculate the required force as,
force = pressure x area = 80 N/m^2 x 5 m^2 = 400 N.
Thus, it takes a force of 400 N (or Newtons), acting over a surface of area 5 m^2, to produce a pressure of 80 N/m^2.
Hope this helps.