In a lead storag battery, Pb (anode) and `PbO_(2)` (cathode) are used. Concentrated `H_(2)SO_(4)` is used as electrolyte. The battery holds 3.5 litre acid with it . In the discharge process, the density of acid fell from 1.294 to 1.139 g/mL. The sulphuric acid of density `1.294" g mL"^(-1)` is 39 % by mass and that of density 1.139 g/mL is 20% by mass.
Equivalent mass of sulphuric acid in lead storage battery is :
A. 49
B. 98
C. `24.5`
D. 196