De Morgan's Laws

Q. If P, Q and R are subsets of a set A, then $R\times (P^c\cup Q^c{)}^c=$

1. $(R\times P)\cap (R\times Q)$
2. $(R\times Q)\cap (R\times P)$
3. $(R\times P)\cup (R\times Q)$
4. $Noneofthese$

Q. Let $n\left(U\right)=700$, $n\left(A\right)=200$, $n\left(B\right)=300$ and $n(A\cap B)=100,\text{then}n(A^c\cap B^c)$ is -

1. $400$
2. $600$
3. $300$
4. $200$

Q. Let $A=\{1,2,3,4\},B=\{2,3,4,5,6\},$ then $A\Delta B=$

1. $\{2,3,4\}$
2. $\left\{1\right\}$
3. $\{5,6\}$
4. $\{1,5,6\}$