If a relation $R$ on the set $\{1,2,3\}$ be defined by $R=\{(1,2)\}$, then $R$ is

Let us define a relation $R$ in $R$ as $a R b$ if $a \geq b$. Then, $R$ is

If $A=\{1,2,3\}$ and consider the relation

$$R=\{(1,1),(2,2),(3,3),(1,2),(2,3),(1,3)\}$$

Then, $R$ is

The identity element for the binary operation $*$ defined on $Q-\{0\}$ as $a * b=\frac{a b}{2}, \forall a, b \in Q-\{0\}$ is

If the set $A$ contains 5 elements and the set $B$ contains 6 elements, then the number of one-one and onto mappings from $A$ to $B$ is