A soap  $\left({\text{C}}_{17}{\text{H}}_{35}\text{COONa}\right)$ solution becomes a colloidal sol at a concentration of $1.2\times {10}^{-3}\text{M}$ . On the average,   $2.4\times {10}^{13}$ colloidal particles are present in $1 {\text{mm}}^3$ . What is the average number of stearate ions  in one colloidal particle (micelle) : Take : Avogadro's number  $=6\times {10}^{23}$