Capacitor. Find thickness of polystyrene

[owtu]

Homework Statement

A 490 pF capacitor consists of two 19 cm -radius circular plates, insulated with polystyrene

Find the thickness of the polystyrene.

Homework Equations

d = (ε_0 * Area * K) / C

The Attempt at a Solution

I converted 490 pF to F

4.90 * 10^-10 F

I converted 19 cm to meters

.19 m

and found the area of the plate

∏r^2 = ∏(.19)^2 = .1134 m^2

K of polystyrene = 2.3, so now just plug everything into my equation

d = ((2.3) * (8.854*10^-12) * (.1134)) / (4.9 * 10^-10)

d = .00471 m

I want my answer in mm with two significant figures

d = 4.7 mm


mastering physics tells me this is the wrong answer, where did I go wrong?

 

[owtu]

never mind, I found it. the value for K was 2.6 not 2.3, I was mistaken