Sputnik I Was Launched into Orbit Around Earth in 1957

Sputnik I was launched into orbit around Earth in 1957.It had a perigee (the closest approach to Earth,measured from Earth's center) of and an apogee (the furthest point from Earth's center) of .What was its speed when it was at its perigee? The mass of Earth is and G = 6.67 × 10^-11 N • m²/kg².

A) 7180 m/s
B) 7840 m/s
C) 8230 m/s
D) 11,000 m/s
E) 13,400 m/s