Reactivity order of halogens towards free radical substitution reaction is:

What is the major product for the below reaction?

${\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_3\underset{\mathrm{hv}}{\overset{{\mathrm{Cl}}_2}{\to }}$ major product.

In given compound, the most reactive hydrogen atom for chlorination is :

Major product of given reaction is :

Order of rate of electrophilic substitution reaction is:

P 

Q 

R 

S