The critical bending compressive stress in the extreme fibre of a structural steel section is $1000 \: MPa$. It is given that the yield strength of the steel is $250 \: MPa$, width of flange is $250 \: mm$ and thickness of flange is $15 \: mm$. As per the provisions of $IS:800-2007$, the non-dimensional slenderness ratio of the steel cross-section is

- $0.25$
- $0.50$
- $0.75$
- $2.00$