Problem: The mass of the Coma cluster of galaxies is 1015 solar masses. Approximately 15% of the mass consists of baryons, the rest is dark matter. Considering that 34 of the baryons are hydrogen, how many hydrogen atoms are in the cluster (the mass of the hydrogen atom is 1.67 10-27 kg)?
A. 10^71
B. 10^72
C. 10^70
D. 10^73