Question: Find the minimum cost spanning tree on the graph above using Kruskal's algorithm. What is the total cost of the tree?
1. **Problem Statement:**
Find the minimum cost spanning tree (MST) of the given weighted undirected graph using Kruskal's algorithm and determine the total cost of the MST.
2. **Kruskal's Algorithm Overview:**
Kruskal's algorithm finds the MST by sorting all edges in ascending order of weight and adding edges one by one to the MST, avoiding cycles.
3. **List of edges with weights:**
- C-B: 12
- B-A: 33
- A-E: 29
- D-E: 14
- C-D: 39
- B-E: 24
- C-A: 20
- D-A: 11
- C-E: 19
- D-B: 32
4. **Sort edges by weight ascending:**
$$D-A=11, C-B=12, D-E=14, C-E=19, C-A=20, B-E=24, A-E=29, D-B=32, B-A=33, C-D=39$$
5. **Select edges for MST:**
- Add $D-A=11$ (no cycle)
- Add $C-B=12$ (no cycle)
- Add $D-E=14$ (no cycle)
- Add $C-E=19$ (no cycle)
- Add $C-A=20$ (check cycle: vertices C, A, E, D connected, adding $C-A$ connects C and A which are already connected through E and D, so this creates a cycle. Skip.)
- Add $B-E=24$ (check cycle: B connected to C, E connected to D and C, adding $B-E$ connects B and E which are already connected through C, so cycle. Skip.)
- Add $A-E=29$ (cycle, skip)
- Add $D-B=32$ (cycle, skip)
- Add $B-A=33$ (cycle, skip)
- Add $C-D=39$ (cycle, skip)
6. **Edges in MST:**
$$D-A=11, C-B=12, D-E=14, C-E=19$$
7. **Check if all vertices connected:**
Vertices: A, B, C, D, E
- $D-A$ connects D and A
- $D-E$ connects D and E
- $C-E$ connects C and E
- $C-B$ connects C and B
All vertices connected.
8. **Calculate total cost:**
$$11 + 12 + 14 + 19 = 56$$
**Final answer:** The total cost of the minimum spanning tree is $56$.