deletions | additions       diff --git a/Problem 2.tex b/Problem 2.tex  index f9d2d67..972b3cf 100644  --- a/Problem 2.tex  +++ b/Problem 2.tex 
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Dense H$_2$ & $5\times10^4$ & 0.0001  \end{tabular}  The total column density is then $\rm{N_H}=(\sum n_H f_V)d\sim0.8~\rm{cm}^{-3}$. As a rough estimate of uncertainty, let's assume $20\%$ errors on the filling factors. The distance $d=8.0\pm0.6~\rm{kpc}$. $d=8.0\pm0.6~\rm{kpc}$ (e.g. \citealt{http://adsabs.harvard.edu/abs/2008ApJ...689.1044G}).