User:SHJX/sandbox2

$$ Y= \textstyle\int_0^\infty e^{-A_0D} f(D)dD $$

$$ Y= e^{-A_cD_0} $$

$$ f(D)= \frac {1}{D_0} exp(\frac {-D}{D_0}) $$ $$ Yexp= \frac {1}{1 + D_0A_0} $$