Answer
The approximate yield strength for the material is $~~300\times 10^6~N/m^2$
Work Step by Step
We can find a general equation for Young's modulus:
$stress = E \times strain$
$E = \frac{stress}{strain}$
On the graph, we can see that the graph is not linear anymore when the stress reaches a value of about $300\times 10^6~N/m^2$
This shows that the stress has exceeded the material's yield strength, and the material is starting to become permanently deformed.
The approximate yield strength for the material is $~~300\times 10^6~N/m^2$
