Recent findings in astrophysics suggest that the observable universe can be modeled as a sphere of radius r = 1.37 x 1010 ly. this is equivalent to 1.3 x 1026 m, with an average total mass density of 1 x 10-26 kg/m3. only about 4% of total mass is due to ‘ordinary’ matter (such as protons, neutrons and electrons). (a)estimate how much ordinary matter (in kg) there is in the observable universe. (b) estimate how much ‘dark matter’ there is in the universe.