F$1812)$ The point masses $m$ and $2m$ lie along the $x-$axis, with $m$ at the origin and $2m$ at $x=L.$ A third point mass $M$ is moved along the $x-$axis. At what position is the net gravitational force on $M$ due to the other two masses equal to zero?

A$)0\mathrm{.}247$

B$)0\mathrm{.}414$ L

C$)0\mathrm{.}797$ L

D$)1\mathrm{.}24LE$