At $298 \text{ K}$,the molar conductivity of $x\% \text{ (w/w)}$ $MX$ solution (aqueous) is $123.5 \text{ S cm}^2 \text{ mol}^{-1}$. The conductance of the same solution is $1.9 \times 10^{-3} \text{ S}$. The value of $x$ is . . . . . . $\times 10^{-2}$. (Given: cell constant = $1.3 \text{ cm}^{-1}$; molar mass of $MX$ is $75 \text{ g mol}^{-1}$,density of aqueous solution of $MX$ at $298 \text{ K}$ is $1.0 \text{ g mL}^{-1}$)

• A
  $10$
• B
  $15$
• C
  $20$
• D
  $25$