The efficiency of a boiler is more if it if provided with mechanical draught rather than

Question

Assertion (A): The efficiency of a boiler is more if it if provided with mechanical draught rather than with natural draught                

Reason (R): The exhaust gasses can be cooled to the lowest possible temperature if mechanical draught is provided.

1. Both A and R are individually true and R is the correct explanation of A
2. Both A and R are individually true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true