It is not called Kaffara but Diyyah. Diyyah is a penalty on the person who kills or injures someone else. It goes to the inheritors of the victim who did not take part in the sinful act itself (abortion).
Deliberate terminating of pregnancy is a sinful act. The Diyyah depends on the age of the embryo. In your case of 11 weeks , the Diyyah is two hundred and ten Mithqal of silver. Every Mithqal is 4.64 grams.