0.5 gm of fuming `H_(2)SO_(4)` (Oleum) is diluted with water. This solution is completely neutralised by 26.7 ml of 0.4 M `NaOH` solution. Calculate the percentage of free `SO_(3)` in the given sample. Give your answer excluding the decimal places.
A. Mass of `SO_(3)` is 0.104 g
B. % of free `SO_(3) = 20 : 7`
C. Normality of `H_(2) SO_(4)` for neutralization is 0.2 N
D. Weight of `H_(2) SO_(4)` is 0.104 g