A spaceship is lanunched into a circular orbit close to the earth's surface. What additional velocity has now to be imparted to the space ship in the orbit to overcome the gravitational pull. (Radius of earth$= 6400 km,g=9.8 m/s^2$)

Question

$$(a)\;\sqrt 2 gR \quad (b)\;\sqrt {2gR} \quad (c)\;\sqrt {gR} \quad (d)\;(\sqrt 2-1) \sqrt {gR}$$