What is the satellite’s altitude above the surface of the earth?

A satellite moves in a circular orbit around the Earth at a speed of 6.1 km/s.
Determine the satellite’s altitude above the surface of the earth. Assume the earth is a homogeneous sphere of radius 6370 km and mass 5.98E24 kg. The value of the universal gravitational constant is 6.67259E-11.
Answer in units of km.