Explanation :
Factored axial load = 2000 kN
As self weight of base plate and steel column is neglected.
Total load on padestal = 2000 kN
Bearing capacity of concrete
= 0.45 x 20 = 9 MPa
Area of steel base plate
$ =\frac{2000\times10^3}{9\times10^6}=2222.22\;\mathrm{cm}^2 $
Side of base plate $ =\sqrt{2222.22}\;=47.14\;\mathrm{cm} $
So, length of base plate will be 48 cm.