Don't solve for wrong answer, i will dislike.

Air flows through a packed bed of a powdery material of $1cm$ depth at a superficial gas velocity of $1c\frac{m}{sec}.$ A manometer connected to the unit registers a pressure drop of $1cm$ of water. The bed has a porosity of $0\mathrm{.}4.$ Assuming that Kozeny$-$Carman equation is valid for the range of study, estimate the particle size of the powder. ${}_{\text{a}\text{i}\text{r}}=1\mathrm{.}23k\frac{g}{m^3}$; ${}_{\text{a}\text{i}\text{r}}=1\mathrm{.}8{10}^{-5}k\frac{g}{m}.sec.$