2018 Pascal Problem 13

A rectangle with height x and width 2x has the same perimeter as an equilateral triangle with side length 10. What is the area of the rectangle?

\textbf{(A)}\ 18\quad \textbf{(B)}\ 50\quad \textbf{(C)}\ 25\quad \textbf{(D)}\ 200\quad \textbf{(E)}\ 100

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 Pascal contests here.