The product of earth's mass (M) and the universal gravitational constant (G) is GM = 3.986 x 10^14 m^3/s^2. The radius of earth is 6371 km. The minimum increment in the velocity to be imparted to a spacecraft flying in a circular orbit around the earth at an altitude of 4000 km to make it exit earth's gravitational field is _______ km/s (round off to 2 decimal places).