JEE Main Chemistry question

The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mhos cm² and at infinite dilution is 400 mhos cm². The dissociation constant of this acid is:

• (A)1.25×10⁻⁴
• (B)1.25×10⁻⁵Correct
• (C)1.25×10⁻⁶
• (D)6.25×10⁻⁴