Consider the two $B^-$ meson decays $B^- \to D^0 K^-$ and $B^- \to \bar{D}^0 K^-$, with $D^0$ and $\bar{D}^0$ decaying to $\pi^+ \pi^-$, so that the final state of these two decays contains the same particles ($\pi^+ \pi^- K^-$).
(a) Draw the corresponding Feynman diagrams.
(b) Determine the dependence of the matrix elements of both decays on the parameters of the CKM matrix taking into account that these parameters are complex numbers.
(c) Estimate the ratio of branching ratios $B(B^- \to D^0 (\to \pi^+ \pi^-)K^-)/B(B^- \to \bar{D}^0 (\to \pi^+ \pi^-)K^-)$ as a function of the Wolfenstein parameters.
