1. The problem is to find a spanning tree from the given grid of quadrilaterals and calculate the total length of the spanning tree edges. 2. A spanning tree connects all vertices (corners) with no cycles and minimum total edge length. 3. The grid has 3 rows and 4 columns of quadrilaterals, so there are 4 columns + 1 = 5 vertical vertices and 3 rows + 1 = 4 horizontal vertices, total 20 vertices. 4. Each quadrilateral has 4 edges with given lengths. We consider all edges between vertices: - Horizontal edges: top and bottom edges of quadrilaterals - Vertical edges: left and right edges of quadrilaterals 5. Extract all edges with their lengths: - Horizontal edges (top row): 6, 3, 5, 6 - Horizontal edges (middle row): 2, 4, 2 - Horizontal edges (bottom row): 7, 5, 2 - Vertical edges (left column): 4, 3, 5 - Vertical edges (middle columns): 6, 2, 7, 4, 2, 2 - Vertical edges (right column): 6, 3, 5, 6, 4, 2 6. Use Kruskal's algorithm to find the minimum spanning tree: - Sort edges by length ascending: 2, 2, 2, 2, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7 - Add edges one by one, avoiding cycles, until all vertices are connected. 7. Select edges: - All edges with length 2 (five edges) - Edges with length 3 (two edges) - Edges with length 4 (three edges) - Edges with length 5 (three edges) - Add one edge with length 6 to connect remaining vertices 8. Calculate total length: $$2+2+2+2+2+3+3+4+4+4+5+5+5+6 = 49$$ 9. Therefore, the length of the minimum spanning tree is $49$ units. Final answer: $49$