Isn't a semi-circle half of a circle? (correct me if I'm wrong) (I'm horrible at math but I might be able to help you figure out what the question is asking) Are there any answer questions we can choose from or is it just a short writing question?
I'm not a math genius but I think that if half of the circle is 0 then the other half is cut up into 3 parts which makes C be 121.666666667........ So the answer would be 121.
