`10 mL` of `0.2 N HCl` and `30 mL` of `0.1 N HCl` to gether exaclty neutralises `40 mL` of solution of `NaOH`, which is also exactly neutralised by a solution in water of `0.61 g` of an organic acid. What is the equivalent weight of the organic acid?
A. 61
B. 91.5
C. 122
D. 183