The simplified switching circuit for the following circuit is

If the sets $A$ and $B$ are defined as $A = \{ (x, y) : y = \frac{1}{x}, x \in R, x \neq 0 \}$ and $B = \{ (x, y) : y = -x, x \in R \}$,then:

If $A = \{3, 6, 9, 12, 15, 18, 21\}$,$B = \{4, 8, 12, 16, 20\}$,$C = \{2, 4, 6, 8, 10, 12, 14, 16\}$,and $D = \{5, 10, 15, 20\}$,find $B - C$.

Let $A$ and $B$ be subsets of a set $X$. Then,

The simplified switching circuit for the following circuit is

If $A = \{ x : x \text{ is a natural number} \}$,$B = \{ x : x \text{ is an even natural number} \}$,$C = \{ x : x \text{ is an odd natural number} \}$,and $D = \{ x : x \text{ is a prime number} \}$,find $C \cap D$.