Orbital radius and speed of a satellite?

Radio and t.v. signals are sent from continent to continent by "bouncing" them from geosynchronous satellites. These satellites circle the Earth once every 24 hours, and so if the satellite circles eastward above the equator, it always stays over the same spot on the earth because the earth is rotating at the same rate. Weather satellites are also designed to hover in this way. What is the orbital radius for such a satellite? What is its orbital speed?

I know that the period T = 86,400 seconds/1 revolution

and I know a few centripetal acceleration equations...but I still don't know what to do here...

I tried solving

2 pi r/ T = sq. root (( G - mass of earth)/r)

but it didn't work out...(Headbang)