 \frac{ (a_0 \beta_0 - b_0 \gamma_0 ) }{\Delta_0} (q_0 q_0^{-n} ) \exp\left( + Y_0 \right) \exp\left( - n Y_s \right) \: + \: \frac{ (-a_0 b_0 + b_0 a_0 ) }{\Delta_0} q_0 \exp\left( + Y_s \right) \nonumber \\ & & \hspace*{0.0in} \: - \: \exp\left( - Y_