The focal length of a thin convex lens for red and violet colour are `44.6cm` and `42.5cm`. Calculate focal length for the mean colour and dispersive power of the lens.
A. Focal length `=43.53cm` dispersive power `=0.048`
B. Focal length `=28.53cm` dispersive power `=0.048`
C. Focal length `=63.53cm`, dispersvie power `=8.48`
D. Foca length `=30.43cm,` dispersive power `=4.8`