55. As shown in the figure, in the Cartesian coordinate system $x O y$, the vertices of the polygon $O A B C D E$ have coordinates $O(0, 0)$, $A(0,6)$, $B(4,6)$, $C(4,4)$, $D(6,4)$, $E(6,0)$. If the line $l$ passes through the point $M(2,3)$ and divides the polygon $O A B C D E$ into two parts of equal area, then the function expression of the line $l$ is $\qquad$
Answer: $y=-\frac{1}{3} x+\frac{11}{3}$