5.1.2 problem 2

Take $\text{Unif}(0,\frac{1}{2})$,

where $C$ is the complete space. Say, $f\left(x\right)>1$ in a given domain $X$
$f\left(x\right)>0$, so ${\int }_{D}f\left(x\right)\mathrm{dx}\le {\int }_{C}f\left(x\right)\mathrm{dx}$
Here ${\int }_{D}1\mathrm{dx}<{\int }_{D}f\left(x\right)\mathrm{dx}$
We can say, $\left|D\right|<1$