There is a power plant in the cell indicated by $C$. The cells indicated by $X$ are places to which the power plant should be connected. This requires electricity masts in some cells, which we can indicate by placing an $M$ in that cell. Two cells with a letter in them can be connected by a cable if the cells are adjacent at a side or a vertex. Ultimately, each cell with an $X$ must be connected to the power plant via one or more cells with the letters $M$ or $X$.