The distance of the satellite form the centre of the earth is 6400 km+600 km=7000 km.
The speed of the satellite is
`sqrt((GM)/a)`
`sqrt(6.67xx10^-11N-m^2/kg^2x6xx10^24kg)/(7000xx10^3m)`
`=7.6xx10^3ms^-=7.6s^-1`
The time period is
`T=(2pia)/v`
`=(2pixx7000xx10^3m)/(7.6xx1063ms^-1)=5.8xx10^3s`.