The length of the projection of the line segment joining the points $(5, -1, 4)$ and $(4, -1, 3)$ on the plane, $x+y+z=7$ is

Question

( A ) $\sqrt{\frac{2}{3}}$
( B ) $\frac{1}{3}$
( C ) $\frac{2}{3}$
( D ) $\frac{2}{\sqrt{3}}$