In a river flowing at $2 \mathrm{~km} / \mathrm{hr}$, a boat travels $32 \mathrm{~km}$ upstream and then returns downstream to the starting point. If its speed in still water be $6 \mathrm{~km} / \mathrm{hr}$, find the total journey time.
(a) 16 hours
(b) 12 hours
(c) 12 hours
(d) None of these