Answer
$f=102.81N$
Work Step by Step
According to Pascal's principle, the pressure of small piston is equal to the pressure of the large piston:
$P_a=P_A$
$\frac{f}{a}=\frac{F}{A}$
$f=F\times \frac{a}{A}$
We plug in the known values in the formula to obtain:
$f=20000\times\frac{\frac{\pi(0.038)^2}{4}}{\frac{\pi(0.53)^2}{4}}$
$f=102.81N$
