AMC 12 2014a Problem 1

What is $10 \cdot \left(\tfrac{1}{2} + \tfrac{1}{5} + \tfrac{1}{10}\right)^{-1}?$

\textbf{(A)}\ 3 \textbf{(B)}\ 8 \textbf{(C)}\ \frac{25}{2} \textbf{(D)}\ \frac{170}{3} \textbf{(E)}\ 170