Capacitors in parallel question

A 10 uF capacitor is charged to 400V. The capacitor is then disconnected from the source of p.d. and connected to an identical, uncharged capacitor. The charge stored by the capacitor is now shared between the two.

1) are they in parallel or series.

I understand they are in parallel, yes?? because the charge has been shared as there are now two paths.

2) calculate their combined capacitance?

so can we assume they both have a capacitance of 10uF??

THIS IS WHAT I AM REALLY STUCK WITH.....
3) calculate the p.d. across each capacitor?

i thought that in parallel the voltage on each capacitor equalled the total voltage. so the answer should be 400V across each! but the answer say's 200V.
WHY!!!

The total charge on the initial capacitor is;
Q = CV = 4000 uc

When the capacitors are connected in parallel, as you describe, the total capacitance is the sum;
Ct = C1 + C2 = 20 uf , since they're identical.

The only thing that is not different is the total charge, since there's no way for any charge to get on or off. But the total charge is now shared between the two capacitors. And from the symmetry (identical capacitors) you can infer that each capacitor has half the total;
q1 = q2 = 2000 uc

Since the capacitors are in parallel they do have equal voltage. But work was done when the charges redistributed and you can't assume the voltage is still 400v.
You can calculate it using the "total" values;
V = Q/Ct = 4000/20 = 200v

Or you can just calculate the voltage on one capacitor(either one);
V = q1/C1 = 2000/10 = 200v