Answer
$150\ kg/m^2$
Work Step by Step
Step 1. As the pressure $p$ on a point in a liquid is directly proportional to the distance $d$ from the surface to the point, we have $p=kd$ where $k$ is a constant.
Step 2. As $p=60\ kg/m^2$ when $d=4\ m$, we have $60=k(4)$, thus $k=15$
Step 3. For $d=10\ m$, we have $p=15(10)=150\ kg/m^2$
