Answer
$A = 134.5 \mathrm{~cm^2}$
Work Step by Step
The minimum area $A$ will be obtained at the minimum separated distance $d$ and when the electric field is maximum, the distance will be the minimum and it calculated by
$$d = \dfrac{V}{E} = \dfrac{5500 \,\text{V}}{1.6 \times 10^{7} \,\text{V/m}} = 3.43 \times 10^{-4} \,\text{m}$$
We could use equation 24.2 in the textbook to determine the area $A$ in the form
\begin{equation}
A = \dfrac{Cd}{K\epsilon_o } \tag{1}
\end{equation}
Let us substitute the values of $\epsilon_o, C, K$ and $d$ into equation (1) to get the value of $A$
\begin{align}
A &= \dfrac{Cd}{K \epsilon_o }\\
& = \dfrac{(1.25 \times 10^{-9} \,\text{F})(3.43 \times 10^{-4} \,\text{m})}{3.6 (8.85 \times 10^{-12} \,\text{F/m})}\\
&= \boxed{134.5 \mathrm{~cm^2}}
\end{align}
