The maximum principal stress is

Question

In a biaxial state of stress, normal stresses are $\sigma _{x} = 900N/mm^{2}$ $\sigma _{y} = 100N/mm^{2}$ and shear stress $\tau = 300N/mm^{2}$. The maximum principal stress is

(a) 800 N/ mm²               (b) 900 N/ mm²

(c) 1000 N/ mm²             (d) 1200 N/ mm²