deletions | additions       diff --git a/Box.tex b/Box.tex  index 397776a..dc0b7b6 100644  --- a/Box.tex  +++ b/Box.tex 
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$N =\overbrace{R}^{\sim10} \times \overbrace{f_p}^{\sim 1} \times \overbrace{n_e}^{\sim 0.2} \times \underbrace{f_l \times f_i \times f_c \times L}_{?}$  So the product of the first 3 terms is now well estblished established  and is is, using a conservtive approximation,  of order 1. So we can simplify the Drake equation and re-write it as as:  $N \approx \underbrace{f_l \times f_i \times f_c \times L}_{?}$