Problem $06\mathrm{.}045-$ Water tank and weight balance

The weight of a water tank open to the atmosphere is balanced by a counterweight, as shown in the given figure. There is a $\backslash (4-\backslash$mathrm$\{$cm$\}\backslash )$ hole at the bottom of the tank with a discharge coefficient of $0\mathrm{.}910,$ and the water level in the tank is maintained constant at $50$ cm by water entering the tank horizontally. Determine how much mass must be added to or removed from the counterweight to maintain balance when the hole at the bottom is opened. Take the density of water to be $\backslash (1000\backslash$mathrm$\{$~kg$\}/\backslash$mathrm$\{$m$\}^\{3\}\backslash ).($Round the final answer to three decimal places.$)$