Three of the Largest Automobile Dealers Agreed Among Themselves as to What

Three of the largest automobile dealers agreed among themselves as to what price they would pay to manufacturers for windshields to put in new vehicles.Would this constitute illegal price-fixing? If so,what kind?

A) No. This is not illegal price fixing.
B) Yes. This is buyers' illegal per se price fixing.
C) Yes. This is sellers' illegal per se price fixing.
D) Yes. This is both buyers' and sellers' illegal per se price fixing.