23. The distance between 2 train stations, \( A \) and \( B \), is 840 km . A train travels from A at a speed of \( 52 \mathrm{~km} / \mathrm{h} \). Another train travels from \( B \) at the same time. What is the speed. in \( \mathrm{km} / \mathrm{h} \), of the \( 2^{\text {nd }} \) train, if the two trains meet 8 hours later?
\[
\leftrightarrow 840 \mathrm{~km} \longrightarrow
\]