A statefinder luminosity distance formula in varying speed of light
  cosmology
  We derive a luminosity distance formula for the varying speed of light (VSL)
theory which involves higher order characteristics of expansion such as jerk,
snap and lerk which can test the impact of varying $c$ onto the evolution of
the universe. We show that the effect of varying $c$ is possible to be isolated
due to the relations connecting observational parameters already by measuring
the second-order term in redshift $z$ unless there is a redundancy between the
curvature and an exotic fluid of cosmic strings scaling the same way as the
curvature.
