**P. 4771.** A graduated cylinder of cross-section \(\displaystyle 50~\rm cm^2\) is filled with some salt solution of density 1.2 g/cm\(\displaystyle {}^3\) up to a height of 10 cm, and then carefully (without mixing the layers) 10 cm-high clean water is stratified onto it.

\(\displaystyle a)\) What is the pressure at the bottom of the cylinder?

\(\displaystyle b)\) What is the total gravitational potential energy of the two samples of liquid with respect to the bottom of the cylinder?

By what amount will these quantities change if the two samples of liquid are mixed? (Neglect the change in the volume of the whole mixture due to the mixing process.)

(4 points)

**Deadline expired on 10 December 2015.**