If permissible working stresses in steel and concrete are respectively 1400 kg/cm2 and 80 kg/cm2 and modular ratio is 18, in a beam reinforced in tension side and of width 30 cm and having effective depth 46 cm, the lever arms of the section, is______________?
A. 37 cm
B. 38 cm
C. 39 cm
D. 40 cm