Answer
Pressure = $\frac{force}{area}$. The pressure is 4% of atmospheric pressure.
$$(0.04)(\frac{101300 N}{m^{2}}) = (force)(100 m^{2})$$
Solve for $force = (0.04)(\frac{101300 N}{m^{2}})(100 m^{2}) = 4 \times 10^{5} N$.
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