In January 2006, astronomers reported the discovery of a planet comparable in size to the earth orbiting another star and having a mass of about 5.5 times the earth's mass. It is believed to consist of a mixture of rock and ice, similar to Neptune. Take mass Earth 5.97* 10^24kg and rEarth = 6.38*10^6m .
If this planet has the same density as Neptune (1.76 ), what is its radius expressed in kilometers? What is its radius expressed as a multiple of earth's radius?