-I and -M group increases rate of reaction.

Nucleophilic aromatic substitution reaction is also known as reaction. To perform reaction benzene ring should have Positive charge on it self. As benzene ring has cloud therefore it self acts as a nucleophile in normal circumstances it cannot undergo reaction. The Essential condition for is "a strong electron withdrawing group must be present at directly attached position of the ring.

in this case group shows effect and generates +ve charge on the benzene ring. In this way Benzene ring behaves as an electrophile and a can easily attack on it to perform Ar reaction.
Mechanism.

Note- group should present at positions not at meta position to perform reaction.
The order of -M effect is

∴ will undergo at fastest rate.