In a structural member under fatigue loading, the minimum and maximum stresses developed at the critical point are $50$ $MPa$ and $150$ $MPa$, respectively. The endurance, yield, and the ultimate strengths of the material are $200$ $MPa$, $300$ $MPa$ and $400$ $MPa$, respectively. The factor of safety using modified Goodman criterion is

- $\dfrac{3}{2} \\$
- $\dfrac{8}{5} \\$
- $\dfrac{12}{7} \\$
- $2$