1998 Fermat Problem 14

Three straight lines, l_1, l_2 and l_3, have slopes \frac{1}{2}, \frac{1}{3} and \frac{1}{4}, respectively. All three lines have the same y-intercept. If the sum of the x-intercepts of the three lines is 36, then the y-intercept is

\textbf{(A)}\ \frac{-13}{12}\quad \textbf{(B)}\ \frac{-12}{13}\quad \textbf{(C)}\ -4\quad \textbf{(D)}\ 4\quad \textbf{(E)}\ -9

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