I'm trying to solve the second statement of the following exercise. It is Exercise 2.5 of "All of Nonparametric Statistics, Larry Wasserman".
My try:
\begin{align} |T(F)-T(G)| &= \left|\int x dF - \int x dG\right| \\ &= \left|\int x d(F-G)\right| \\ &\leq \int |x|d(|F-G|) \\ &\leq M \int d(|F-G|) \\ &\leq M \sup_{x}|F(x)-G(x)| \end{align}
I can not verify the last inequality. Is it true?