deletions | additions       diff --git a/Box.tex b/Box.tex  index 7f54544..a77eae1 100644  --- a/Box.tex  +++ b/Box.tex 
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So the product of the first 3 terms is now well established and is, using a conservative approximation, of order 1.   $N =\underbrace{\overbrace{R}^{\sim10} =\underbrace{\overbrace{R}^{\approx10}  \times \overbrace{f_p}^{\sim \overbrace{f_p}^{\approx  1} \times \overbrace{n_e}^{\sim \overbrace{n_e}^{\approx  0.2}}_{\sim 5} \times \underbrace{f_l \times f_i \times f_c \times L}_{?}$ We can then simplify the Drake equation and re-write it as: