A W21 x 57 of A992Gr50 steel column having length of 6 m and is fixed at both ends. (Gr50 steel = 50 ksi = 345 MPa = Fy) is used to carry a load of 900 kN dead load and 400 kN live load. Note: Use NSCP 2015 Properties of W21 x 57 A 10800 mm d = 536 mm br = 167 mm tr = 16.5 mm tw 10.3 mm Kdes = 29.2 mm rx = 212 mm Ry = 34.3 mm a. Calculate the critical slenderness ratio of the W section if the column is braced at midpoint of the weak axis b. Calculate the compressive capacity of built-up section using ASD and LRFD c. Calculate the demand-capacity factor, Is the section adequate?