  We show that the Kronecker coefficients (the Clebsch-Gordan coefficients of
the symmetric group) indexed by two two-row shapes are given by quadratic
quasipolynomial formulas whose domains are the maximal cells of a fan. Simple
calculations provide explicitly the quasipolynomial formulas and a description
of the associated fan.
  These new formulas are obtained from analogous formulas for the corresponding
reduced Kronecker coefficients and a formula recovering the Kronecker
coefficients from the reduced Kronecker coefficients.
  As an application, we characterize all the Kronecker coefficients indexed by
two two-row shapes that are equal to zero. This allowed us to disprove a
conjecture of Mulmuley about the behavior of the stretching functions attached
to the Kronecker coefficients.
