45) If the velocity of water layers in river is given by v = ky² , where y is the height from the river bed. The force required to keep a square plate of area A with constant velocity at height h is $[ \eta =coefficient of vis\cos ity] is$
$$\begin{gathered} \left(1\right) \eta Ak\frac{h}{2} \\ \left(2\right) 4\eta Akh \\ \left(3\right) 2\eta Akh \\ \left(4\right) \eta Akh \end{gathered}$$