A person reaches a point directly opposite on the other bank of a river. The velocity of the water in the river is 4 $ms^{-1}$ and the velocity of the person in still water is 5 $ms^{-1}$. If the width of the river is 84.6 m , time taken to cross the river in seconds is

Question

$\begin {array} {1 1} (1)\;28.2 & \quad (2)\;9.4 \\ (3)\;2 & \quad (4)\;84.6 \end {array}$