A boat is steered with constant velocity u .It starts from Point A on the bank of a river of width 12*(2)^(1/2)m which flows at a constant speed of u/2.The boat is always steered such that it point towards a fixed point B on the other bank directly opposite to A.Find the distance of the boat from point B when the line joining boat and point B makes an angle of 45 degrees with the line AB.