An organic compound A having molecular formula C₆H₆O gives a violet colour with neutral FeCl₃ ​ solution. A on treatment with CO₂​ and NaOH at 400 K under pressure gives B which on acidification gives a compound C. The compound C reacts with acetyl chloride to give D which is popular pain killer. Deduce the structure of A, B, C and D.

What is the total number of carbon atoms in compound D?

9