An aircraft of mass `4 xx 10^(5)kg` with total wing area `500m^(2)` in level flight at a speed of 720 km h^(-1)`. The density of a at its height is `1.2 kgm^(-3)`. The fractional increases in the speed of the air on the upper surface of its wings relative to the lower surface is (take `g = 10 ms^(-2)`)