Continuation of Problems 2 and 39, another explanation is that the stones move only when the water dumped on the playa during a storm freezes into a large, thin sheet of ice. The stones are trapped in place in the ice. Then, as air flows across the ice during a wind, the air-drag forces on the ice and stones move them both, with the stones gouging out the trails, the magnitude of the air-drag force on this horizontal "ice sail" is given by D_ice = 4C_icepA_ice v²,where C_ice is the drag coefficient (2.0 x 10^-3), p is the air density (1.21 kg/m³), A_ice is the horizontal area of the ice, and v is the wind speed along the ice. Assume the following: The ice sheet measures 400m by 500m by 4.0mm and has a coefficient of kinetic friction of 0.10 with the ground and a density of 9I7 kg/m³. Also assume that 100 stones identical to the one in Problem 2 arc trapped in the ice. To maintain the motion of the sheet, what are the required wind speeds? 

(a) Near the sheet and

(b) At a height of 10 m?

(c) Are these reasonable values for high-speed winds in a storm?