The state of stress at a point under plane stress condition is $$\sigma_{xx} = 40 \: MPa, \: \: \sigma_{yy} = 100 \: MPa \: \: \text{and }\tau_{xy} =40 \: Mpa$$ The radius of the Mohr's circle representing the given state of stress in $MPa$ is
- $40$
- $50$
- $60$
- $100$