AMC 12 2008b Problem 10

Bricklayer Brenda would take $9$ hours to build a chimney alone, and bricklayer Brandon would take $10$ hours to build it alone. When they work together they talk a lot, and their combined output is decreased by $10$ bricks per hour. Working together, they build the chimney in $5$ hours. How many bricks are in the chimney?

(Solution)

\textbf{(A)}\ 500 \textbf{(B)}\ 900 \textbf{(C)}\ 950 \textbf{(D)}\ 1000 \textbf{(E)}\ 1900