A steel rod of sectional area 250 sq. mm connects two parallel walls 5 m apart. The nuts at the ends were tightened when the rod was heated to 100°C. If steel = 0.000012/C°, Esteel = 0.2 MN/mm2, the tensile force developed at a temperature of 50°C, is_________________?
A. 80 N/mm2
B. 100 N/mm 2
C. 120 N/mm2
D. 150 N/mm2