Problem 131:
Given a point $B$, a point $M_{a}$ and a point $M_{b}$, construct the triangle ABC.

Construction: 
1. Using the point $B$ and the point $M_{a}$, construct a point $C$ (rule W01);
2. Using the point $B$ and the point $M_{b}$, construct a point $G$ (rule W01);
3. Using the point $M_{a}$ and the point $G$, construct a point $A$ (rule W01);
4. Using the point $B$ and the point $C$, construct a point $\_M_{a}$ (rule W01);
5. Using the point $C$ and the point $A$, construct a point $\_M_{b}$ (rule W01);

Statement:
Prove that the point $B$ is identical to the point $B$.

