**Key concept to solve this:**

**Potential Energy Function: ** If a force acting on an object is a function of position only, it is said to be a conservative force, and it can be represented by a potential energy function which for a one-dimensional case satisfies the derivative condition

**-dU/dx = F(x)**

We have given U = 20xy/ z

Now taking the derivative of U w.r.t x,y and z we get,

F_{x} = -20y/z, F_{y} = -20x/z, and F_{z} = 20xy/z^{2}

Now adding all we get the final force, i.e

**F = -(20y/z)i-(20x/z)j+(20xy/z**^{2})k.