A wind with speed 40m/s blows parallel to the roof of a house. The area of the roof is 250m². Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the force will be (Pair=1.2kg/m³)
A, 4.8×10⁵N, downward
B, 4.8×10⁵N, upward
C, 2.4×10⁵N, upwards
D, 2.4×10⁵N, downwards