$(7\mathrm{.}5$ pts$)$ A U$-$tube manometer is connected to a closed tank containing air and water. At the closed end of me manometer the pressure is $1\mathrm{.}3$ psig $.$ Determine the pressure reading in the gage $($in $l\frac{b}{f}{t}^2)$ for a manometer differential reading of $4$ ft $.$ Take $$ of the gage fluid $=90l\frac{b}{f}{t}^3.$