What does this mean How to solve

A vertical tank is $1\mathrm{.}8$ meters tall $)=(1\mathrm{.}8m,$ filled with water and oil. Due to the difference in densities, the water is on the bottom and the oil is on top. The tank is open at the top. Water occupies $65\%$ of the tank$\text{'}$s height, while the remaining $35\%$ is filled with oil $($density of $850k\frac{g}{m^3}).$ If the tank is located in Denver, Colorado $($altitude of $5,280$ feet$),$ compute the pressure distribution within the tank. Specifically, you'll need to figure out the pressure at four key spots:

a$)$ Top of the tank $z=0\%H$

b$)z=25\%H$

c$)z=75\%H$

d$)$ Bottom of the tank $z=100\%H$