the final mle estimates are :
coefficient standard-error t-ratio
beta 0 0.19030895E+01 0.27109217E-01 0.70200830E+02
beta 1 0.35251085E+00 0.27054170E-02 0.13029816E+03
beta 2 0.12937028E+00 0.22818576E-02 0.56695157E+02
beta 3 0.70059508E+00 0.23203092E-02 0.30194039E+03
sigma-squared 0.13438009E+02 0.13998667E+00 0.95994925E+02
gamma 0.91350586E+00 0.13761455E-02 0.66381488E+03
mu -0.70073391E+01 0.10974152E+00 -0.63853129E+02
eta is restricted to be zero
log likelihood function = -0.37077529E+06
LR test of the one-sided error = 0.19222301E+05