A fast train takes 3 hrs less than the a slow train for a journey of $600\;km$. If the speed of the slow train is 10km/hr less than that of the fast train, find the speeds of the two trains

Question

$\begin{array}{1 1} 40\;km/hr\; and\;50\;km/hr \\ 44\;km/hr\; and\;56\;km/hr \\ 56\;km/hr\; and\;80\;km/hr \\ 30\;km/hr\; and\;50\;km/hr \end{array}$