Fixed typo in variation function.

src/fa/rs/bv.tex

@@ -29,7 +29,7 @@
     is the \textbf{variation function} of $f$ with respect to $\rho$, and:
     \begin{enumerate}
         \item $T_{f, \rho}: [a, b] \to [0, \infty]$ is a non-negative, non-decreasing function. 
-        \item If $f \in BV([a, b]; E)$, then for any $[c, d] \subset [a, b]$, $[f]_{\text{var}, \rho} = T_{f, \rho}(d) - T_{f, \rho}(a)$. 
+        \item If $f \in BV([a, b]; E)$, then for any $[c, d] \subset [a, b]$, $[f]_{\text{var}, \rho} = T_{f, \rho}(d) - T_{f, \rho}(c)$. 
     \end{enumerate}
 \end{definition}
 \begin{proof}