def mk2mass_ben_poly(mk):
  """mk2mass_ben_poly - M_K to mass, Benedict et al. (2016) polynomial.

Usage:

  mass = mk2mass_ben_poly(mk)

Where mk is absolute 2MASS K magnitude and mass is in solar masses.

This version is the original polynomial "reverse model" (absolute
magnitude to mass) from the paper, for comparison purposes.

NOTE: the range of the parameters is not checked to ensure the
relation is used within the domain of applicability, this is left to
the user.

References:

Benedict et al. (2016) AJ 152 141

"""

  arg = mk - 7.5
  mass = (((-0.0032*arg + 0.0038) * arg + 0.0400) * arg - 0.1352) * arg + 0.2311
  return mass