A metal rod of 30 cm length expands by 0.075 cm when its temperature is raised from 0∘C to 100∘C. Another rod of different metal of length 45 cm expands by 0.045 cm for the same rise in temperature. A composite rod C made by joining A and B end to end expands by 0.040 cm when its length is 45 cm and it is heated from 0∘C to 50∘C. Find the length of each portion of the composite rod.