  Moller Scattering and Bhabha Scattering on noncommutative space-time is
restudied. It is shown that the noncommutative correction of scattering cross
sections is not monotonous enhancement with the total energy of colliding
electrons, there is an optimum collision energy to get the greatest
noncommutative correction. Most surprisingly, there is a linear relation
between the noncommutative QED threshold energy and the optimum collision
energy.
