Calculate capacitance of a parallel plate but of made up of two media

[BeeDee10]

Homework Statement

Calculate capacitance of a parallel plate but of made up o two media!?
The parallel plate capacitor in the figure below is quarter-filled with mica (εr=6). Its remaining ¾ part is filled with air. The total area of the capacitor is 10 cm2 and the distance separating the plates is 2mm. Find the capacitance of this capacitor.
This is the figure: http://postimg.org/image/p2hdvdvld/
Please show steps.
Even my teacher couldn't solve this question correctly, she says we need to have the charge.

Homework Equations

The Attempt at a Solution

 

[bigQ]

You can imagine the given situation like this: two capacitors with plate area 5 cm² and having plates 1mm apart in series (one of which is filled with mica). Now these two are in parallel with cap. with area 5 cm2 and separation 2mm. You don't need to know charge. Just use the formula C= εA/d

 

[SammyS]

Now, with that wonderful hint, we expect BeeDee10 to post a response which indicates some progress towards solving the problem -- before anyone else offers any help.