15. A 5.00 x 102kg communications satellite is to be placed into a circular geosynchronous orbit around the Earth. a) What is the radius of the satellite's orbit? [3 marks] b) What is the gravitational potential energy of the satellite when it is attached to its launch rocket, at rest on Earth's surface? [2 marks] c) What is the total energy of the satellite when it is in geonsynchronous orbit? [3 marks] d) How much work must the launch rocket do on the satellite to place it into orbit? [2 marks]