Answer
$C=35pF$
Work Step by Step
We know that $C=\frac{A\epsilon_{\circ}}{d}$
We are given that $A=4 cm^2=4\times10^{-4}m^2$ and $d=1mm=1\times10^{-3}m$
Thus, we obtain:
$C=\frac{4\times10^{-4}(8.85\times10^{-12})}{1\times10^{-3}}$
$C=3.5\times10^{-12}=35pF$
$C=35pF$
