Compound which rotates the plane polarised light is known as optically active compound . On the basis of direction of rotation two forms of an optically active compounds are termed as dextro and laevo rotatory . The two are termed as enantiomers . If we have a 1 : 1 mixture of d and l isomers of a given chiral compound , optical rotation of such mixture is zero Such a mixture is optically inactive and is called a recemic modification. The net specific rotation of any mixture of the d and isomers of a given chiral compound is equal to the weighted average of the rotations due to both the isomers Mathematically if can be expressed as : `[alpha]_(net) =f_(d) [alpha_(d)] + f_(1) [alpha_(l)]` Where `f_(a)` and `f_(l)` are fractions of d and l isomers respectively and `[alpha_(d)] , [alpha_(l)]` are their specific rotations The pure of isomer of certain chiral compound has `[alpha]_(d)^(25) =+ 55^(@) .A` non racemic mixture of this compound has a net `[alpha]_(d)^(25) =- 11^(@) .` What is the fractions of this isomer in mixture ?A. 0. 40B. 0.6C. 0.3D. 0. 70