<image>As shown in the figure, diagrams ①②③④ are called planar graphs. Observe figure ① and the corresponding values in the table, explore the counting method and provide answers.

(1) Count the number of vertices and edges each diagram has, and how many regions these edges enclose, then fill in the results into the table:
 \frac{     }(2) Based on the values in the table, write a relationship between the number of vertices m, edges n, and regions f of the planar graph:____.
(3) If a planar graph has 20 vertices and 11 regions, then using the relationship obtained in (2), the planar graph has ____ edges.