How Do You Solve This Capacitor Problem with Aluminum Electrodes?

[RED119]

Homework Statement

Two 5.0-cm-diameter aluminum electrodes are spaced 0.50 mm apart. The electrodes are connected to a 200 V battery.

Homework Equations

C = εA/d

The Attempt at a Solution

So for my solution I took the area of the plate, ((.05²π) * 8.85*10^-12) / .5*10^-3 and I got an answer of 1.39 * 10^-10 F or 139 pF. The website the homework is done through is saying this is wrong. not too sure where the mistake is...

 

[magoo]

Area of electrode = pi * d^2 /4

Looks like you used pi * d^2