Let $\displaystyle B$ be an arbitrary Borel set of finite Lebesgue measure with $\displaystyle B \subset \mathbb{R}$. Show that for every $\displaystyle \epsilon >0$ there exists a finite union of disjoint intervals $\displaystyle A = (a_1,b_1] \cup (a_2,b_2] \cup...\cup (a_n,b_n]$ such that the Lebesgue measure of $\displaystyle A \triangle B$ is less than $\displaystyle \epsilon$.