Since ½Tp is very long then lp = 0

 Therefore le = lb = l

 Also l(A) = 1.5 l(D)

 For Aristophanes:
NA = 2N0e-l(A) t = 2N0e-1.5l(D)t

 For Demetrius:
ND = N0 = N0e-l(D)t

 When NA = ND
2N0e-1.5l(D)t = N0e-l(D)t

 Taking natural logarithms:
ln 2 - 1.5 l(D) t = -l(D) t

 0.5 l(D) t = ln 2
t = ln 2/(0.5)(0.10) = 14 days

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