Consider a U$-$tube whose arms are open to the

atmosphere. Now equal volumes of water $(=1000\frac{kg}{m^3})$

and light oil $(\{$:$=789\mathrm{.}7\frac{kg}{m^3})$ are poured from different

arms. A person blows from the oil side of the U$-$tube until

the contact surface of the two fluids moves to the bottom

of the U$-$tube, and thus the liquid levels in the two arms

are the same. If the fluid height in each arm is $76$ cm $,$

determine the gage pressure the person exerts on the oil

by blowing.