9 volumes of a gaseous organic compound A and just sufficient amount of oxygen required for its complete combustion, yielded, 4 volume of `CO_2`, 6 volumes of water vapour and 2 volumes of `N_2`, all volumes measured at the same temperature and pressure. If the compound A contained only C,H and N,
(i) how many volumes of oxygen are required for complete combustion, and
(ii) what is the molecular formula of the compound A ?