Maximum Number of Arcs in Digraph/Examples/Order 4

Examples of Use of Maximum Number of Arcs in Digraph
Let $D$ be the digraph of order $4$ whose edge set $E$ is as large as possible.

Then the number of arcs of $G$ is given by:
 * $\size E = 12$

Proof
By Maximum Number of Arcs in Digraph:
 * $\size E = 4 \times \paren {4 - 1} = 12$