1-chloro-2-methylbutane undergoes reaction with Cl2 by a radical substitution mechanism to yield a mixture of products, among which are 1,4-dichloro-2-methylbutane and 1,2-dichloro-2- methylbutane a)

1-chloro-2-methylbutane undergoes reaction with Cl2 by a radical substitution mechanism to yield a mixture of products, among which are 1,4-dichloro-2-methylbutane and 1,2-dichloro-2- methylbutane 

a) Predict which one of the two products is optically active and inactive compounds. 

b) Provide stepwise mechanism which involved initiation, propagation and termination steps for the production of 1,4-dichloro-2-methylbutane or 1,2-dichloro-2-methylbutane.