A boat crosses a river at velocity $ \xrightarrow { v } $ (relative to water ) that is constant relative to water and perpendicular to the banks. the magnitude of the velocity $ \xrightarrow { V } $ is0.3 m/s . width of the river b=63 m. speed of the current varies according to the parabolic law. $ u\quad =u_{ 0 }-\dfrac { 4u_{ 0 } }{ b^{ 2 } } \left( x-\dfrac { b }{ 2 } \right) ^{ 2 } $ where x is distance from the banks and $ u_0 $ is constant equal to 5 //s. choose correct options.