c0       = -12052.5
  c1 (age) = 257.735
  c2 (sex) = -128.64
  c3 (bmi) = 322.364
  c4 (kid) = 474.411
  c5 (smo) = 23823.4
  Total sum-of-squares error is 4.9073e+10
  Bill =   15820.69, Estimate =   25661.86, Error =   -9841.17
  Bill =   27808.72, Estimate =   36225.45, Error =   -8416.73
  Bill =    1837.23, Estimate =    1120.43, Error =     716.80
  Bill =   37701.88, Estimate =   31298.20, Error =    6403.68