I have a hard time with determining the input impedance of the problem shown as well as the equivalent lumped circuit model with this Zin
The wavelength is 2e8 /(400e6) = 0.5 m
Hense, the transmission line is 2.4 wavelengths (eq 0.4 wavelengths) and the load is 75 / 50 = 1.5. 

So the result is z_nom= 1.04 + 0.41j

Smithchart