A Ketone (A) gives positive iodoform test. (A) On reduction with Lithium Aluminimum Hydride gives (B) which on heating with phosphoric acid gives (C).
(C) On reaction with Ozone in presence of zinc water gives acetaldehyde and acetone.
Give the total number of atoms present in (A),(B) And (C).
Illustratively if suppose (a) is CH4 then total atoms = 5.
So you need to sum up the total atoms present in A) , B) And C).