A dam retains a lake $6 \mathrm{~m}$ deep, as shown in Fig. P1.97. To construct a gate in the dam, we need to know the net horizontal force on a $5-\mathrm{m}$ -wide, $6-\mathrm{m}$ -tall port section that then replaces a $5-\mathrm{m}$ section of the dam. Find the net horizontal force from the water on one side and air on the other side of the port.