Electric field with dielectric constant

[quietriot1006]

Homework Statement

Two 5.0mm*5.0mm electrodes with a 0.10mm thick sheet of Mylar between them are attached to a 9.0 V battery. Without disconnecting the battery, the Mylar is withdrawn. (Very small spacers keep the electrode separation unchanged.) Dielectric constant for Mylar is k=3.1. What is the charge before and after the Mylar is withdrawn?
What is the electric field before and after the mylar is withdrawn?

Homework Equations

C={k(epsilon_o)A}/d
Q=CV
C=kC_o

The Attempt at a Solution

I get the charges correctly but i just can't get the electric field before and after. Charge before is 62 pC and after its 20 pC. Help please.

 

[TSny]

The electric field E is uniform between the two "plates". There is a simple relation between V, E, and the distance d between the plates.