4. Function
$$
\begin{aligned}
y= & |x-1|+|2 x-1|+|3 x-1|+ \\
& |4 x-1|+|5 x-1|
\end{aligned}
$$

achieves its minimum value when the variable $x$ equals ( ).
(A) $\frac{1}{4}$
(B) $\frac{1}{3}$
(C) can take any real number from $\frac{1}{4}$ to $\frac{1}{3}$ (including $\frac{1}{4}$ and $\frac{1}{3}$)
(D) can take any real number from $\frac{1}{3}$ to $\frac{1}{2}$ (including $\frac{1}{2}$ and $\frac{1}{3}$)