The force exerted by a pressure of any gas over a surface its given by the formula P=F/S (where P is pressure, F force and S surface).
We can multiply both sides of the formula by S to obtain the force.
P*S=(F*S)/S
P*S=F
Solve for P=1.80*10^5 Pa and S=4.10*10^-4 m^2 ([Pa] =[N/m^s])
(1.80*10^5 N/m^s) * (4.10*10^-4 m^2) =F
73.8 N =F