Motion

A boat crosses a river from part \(A\) to part \(B\), which are just on the opposite side. The speed of the water. \(v_\omega\) and the of boat is \(v_B\) relative to still water. Assume \(v_B=\sqrt{2} v_\omega\). What is the time taken by the boat, if it has to cross the river directly on the \(A B\) line (\(D=\) width of the river) ?