Partners

I have started revising for my exam (11 June) and I am just reading an article in PQ Magazine that I saved from January called “are you ready for F4?” page 18 and 19

I have been working through the questions in the article, but do not understand Q5, was wondering if someone could explain.

it says:-

Wang has sued Xia, a partner in an ordinary partnership, for a debt of £1000 in respect of goods supplied to the firm by Wang.
It has transpired that Xia cannot satisfy the whole judgement debt but he has managed to pay Wang £800
Wang now wishes to sue the other 10 partners.

How much can she sue each of them for?
A £20
B £100
C £200
D £1000
E Nothing since her action against Xia means that she now cannot sue another partner

I put £200, but the answer says it is D £1000

Confused, if Xia has already paid £800, why is the answer £1000?, am I reading the question wrong?

Any help much appreciated.