Two identical thin metal strips one of aluminium and the other of iron are riveted together to form a bimetallic strip. The temperature is raised by `50^(@)C`. If the central planes of the two strips are separated by 2nm and the coefficients of thermal expansion of aluminium and iron are respectively `30 xx 10^(-6)//^(@)C` and `10 xx 10^(-6)//^(@)C` the average radius of curvature of the bimetallic strip is about
A. 50 cm
B. 100 cm
C. 150 cm
D. 200 cm
