What is the charge on the left-hand plate of C4?

[driedupfish]

The capacitors in the circuit below are all identical. The EMF of the battery is unknown.
http://online.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys212/oldexams/exam1/sp08/fig24.gif

If the charge on the left-hand plate of C1 is +24 μC, what is the charge on the left-hand plate of C4?

(a) Q4 = -24 μC
(b) Q4 = -12 μC
(c) Q4 = 0
(d) Q4 = +12 μC
(e) Q4 = +24 μC

What's the concept behind this? Is it -24 uC because the left plate of C4 is next to the negative terminal of the battery?

 

[rl.bhat]

Only two left plates are connected directly to E. According to conservation of charges the charges on two plates must be equal and opposite.