Density of a Bok globule having a radius of 1 lightyear and mass of 100M?

Find the density in atoms per cubic entimeter of a Bok globule having a radius of 1 light year and a mass of 100 M. how does your result compare with the desnity of a typical H II region, between 80 and 600 atoms per cm^3? (Assume that the globule is made purely of hydrogen atoms).

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