The rowing speed of a man in still water is \(7.5\,\text{kmph.}\) In a river flowing at \(1.5\,\text{kmph,}\) it takes the same boatman \(50\) minutes to row a certain distance and come back. Find the distance (one way).
A. \(1\,\text{km}\)
B. \(2\,\text{km}\)
C. \(3\,\text{km}\)
D. \(4\,\text{km}\)
E. \(6\,\text{km}\)
OA C