In a surface mine, third bench from the pit bottom is blasted, as shown in the figure. The width, height and slope angle of each bench are 8 m, 6 m, and 80°, respectively. A fly rock is projected at an angle of 45° with the horizontal with initial velocity, v. If the acceleration due to gravity is 10 m/s² then the minimum velocity (v) in m/s required for the fly rock to reach just beyond toe of the pit slope is _____.