A rectangular water tank is divided by a partition into two chambers as shown in the figure. In the bottom of the partition is a round, sharp$-$edged orifice with a diameter of $162$ mm$.$ The coefficient of discharge for the orifice is $0\mathrm{.}55,$ at a certain instant, the water level in chamber B is $2\mathrm{.}5$ m higher than it is in chamber A$.$ How long will it take for the water surfaces in the two chambers to be at the same level? Answer in s