Suppose that the range of the continuous variables $X$ and $Y$ is $0<x<a$ and $0 < y < b$. Also suppose that the joint probability density function $f_{X Y}(x, y)=g(x) h(y),$ where $g(x)$ is a function only of $x$ and $h(y),$ is a function only of $y .$ Show that $X$ and $Y$ are independent.