A planar graph has, $\large\color{maroon}{\text{k}}$ connected components $\large\color{maroon}{\text{v}}$ vertices $\large\color{maroon}{\text{e}}$ edges If the plane is divided into $\large\color{maroon}{\text{r}}$ ... $\large\color{maroon}{\text{v}}$ , $\large\color{maroon}{\text{e}}$ and $\large\color{maroon}{\text{r}}$ ?

How many planar regions? How many closed regions? and how many are unbounded? How many of then are bounded by a cycle of length $4$ ? Now, for example (a different question, not related to above diagram ) a question says, In a connected 3 regular graph, every planar region is bounded by exactly 5 edges, then count no of edges? Please explain the last QS with the help of Euler's equation.