$8\mathrm{.}13$ A tower, $0\mathrm{.}6m$ diameter, packed with $50-mm$ ceramic Raschig rings to a depth of $1\mathrm{.}2m,$ is to be used for producing a solution of oxygen in water for certain pollution$-$control operations. The packed space will be pressurized at $5std$ atm abs with pure oxygen gas from a gas cylinder. There is to be no gas outlet, and gas will enter from the cylinder only to maintain pressure as oxygen is dissolved. Water will flow down the packing continuously at $1\mathrm{.}50k\frac{g}{s}.$ The temperature is to be $25C.$ Assuming that the entering water is oxygen$-$free, what concentration of oxygen can be expected in the water effluent?