Suppose \(ABOC\) is a rhombus in the first quadrant with \(O\) being the origin. If the vertices \(B\) and \(C\) of \(\triangle ABC\) lie respectively on
\[
y=\frac{4}{3}x
\]
and
\[
y=0,
\]
and the side \(BC\) passes through
\[
\left(\frac23,\frac23\right),
\]
then the midpoint of \(BC\) is