Calculating the capacitance of a parallel-plate air capacitor

[shandsy]

Homework Statement

A parallel-plate air capacitor is made by using two plates 18 cm square, spaced 3.5 mm apart. It is connected to a 3-V battery.

What is the capacitance?

Homework Equations

C = ε_o(A/d)

The Attempt at a Solution

ε_o = 8.854e-12
A = .18 m
d = .0035 m

C = ε_o (.18/.0035) = 4.55348571e-10 F

This is coming up as the wrong answer. I have no idea what I'm doing wrong.

 

[shandsy]

Never mind, I solved the problem. I read "18 cm square" to mean 18 cm², but I guess it really meant a square with 18cm sides, so A = .0324 m². Sorry about that!