$1-[1$ mark$]$ Saline water enters a tank at a rate of $2\mathrm{.}8\frac{m^3}{s}$ and a concentration of $5\mathrm{.}2k\frac{g}{m^3}$ and leaves at the same volumetric flow rate $2\mathrm{.}0\frac{m^3}{s}$ at $t=0.$ Calculate the initial rate of salt out from the tank in $k\frac{g}{m}in.$