AMC 8 2013 Problem 18

Isabella uses one-foot cubical blocks to build a rectangular fort that is $12$ feet long, $10$ feet wide, and $5$ feet high. The floor and the four walls are all one foot thick. How many blocks does the fort contain?

$\textbf{(A)}\ 204 \textbf{(B)}\ 280 \textbf{(C)}\ 320 \textbf{(D)}\ 340 \textbf{(E)}\ 600$