$$A$$ and $$B$$ are non-singleton sets and $$n(A \times B)=35$$. If $$B \subset A$$, then $${ }^{n(A)} C_{n(B)}$$ is equal to

A student has to answer 10 questions, choosing at least 4 from each of the parts $$A$$ and $$B$$. If there are 6 questions in part $$A$$ and 7 in part $$B$$, then the number of ways can the student choose 10 questions is

The value of $${ }^{16} C_9+{ }^{16} C_{10}-{ }^{16} C_6-{ }^{16} C_7$$ is

The number of 4 digit numbers without repetition that can be formed using the digits $$1,2,3,4,5,6,7$$ in which each number has two odd digits and two even digits is