2000 Gauss 7 Problem 23

The total area of a set of different squares, arranged from smallest to largest, is 35 km^2. The smallest square has a side length of 500 m. The next larger square has a side length of 1000 m. In the same way, each successive square has its side length increased by 500 m. What is the total number of squares?

\textbf{(A)}\ 5\quad \textbf{(B)}\ 6\quad \textbf{(C)}\ 7\quad \textbf{(D)}\ 8\quad \textbf{(E)}\ 9

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Gauss contests here.