Read the paragraph carefully and answer the following questions: During gas analysis, the eudiometer tube filled with mercury is inverted over a trough containing. mercury. A known volume of the gas. or gaseous mixture to be studied is next introduced, which displaces an equivalent amount of mercury. Next a known amount, of oxygen in excess is introduced and the electric spark is passed, whereby the combustible material gets oxidized. The volume of carbon dioxide, water vapour or other gaseous products of combustíon are next determined by absorbing them in suitable reagents. The various reagents used for absorbing different gases areO_(3) rarr turpentine oil O_(2) rarr alkalino pyragallol CO_(2), SO_(2) rarr alkali solution [NaOH,KOH,Ca(OH)_(2)] In a solid 'AB' having a NaCl structure, A atoms occupy the coners of the cubic unit cell. If all the face centred, atoms alonig one of the axes are removed, then the resultant stoichiometry of the solid is