v^2 = u^2 - 2gh; where v is the final speed, u is the initial speed, g = 9.8 m/s = 0.54 ft/min is the accerelation due to gravity, h = height.
At the maximum height, the final speed is 0.
u^2 = 2gh = 2 x 0.54 x 36 = 38.58
u = sqrt(38.58) = 6.21 ft/min
Therefore, the stne should be thrown with 6.21 ft/min