  In these lectures we give, first, the model-independent analysis of the
exclusive rare decays B -> K l(bar) l and B_c -> D(D*) l(bar) l with special
emphasis on the cascade decay B_c -> D(*)(-> D pi) l(bar) l. We derive a
four-fold angular decay distribution for this process in terms of helicity
amplitudes including lepton mass effects. The four-fold angular decay
distribution allows to define a number of physical observables which are
amenable to measurement. Second, we calculate the relevant form factors within
a relativistic constituent quark model, for the first time without employing
the impulse approximation. The calculated form factors are used to evaluate
differential decay rates and polarization observables. We present results on a
set of observables with and without long-distance contributions. and compare
them with the results of other studies.
