Hi , I don't know if I am write , but i think the answer should be
3C2 * 4C2
For example let part B has 4 questions namely X,Y,W,Z ...then attempting 2 questions say X and Z is same as Z and X , we should not consider it as 2 different choices .... so its no 4C2 , it should be 4P2
3* 6 = 18