A motorboat goes downstream in river and covers a distance between two coastal towns in 5 hours. It covers this distance upstream in 6 hours. If the speed of the stream is $3 km/hr$. Find the speed of the boat in still water

Question

$\begin{array}{1 1} 30\;km/hr \\ 31\;km/hr \\ 32\;km/hr \\ 33\;km/hr \end{array}$