Due to recent significant cost increases, several competing road construction businesses decided to allocate construction projects among themselves based upon historic market share. Under the arrangement, a company would be designated to submit a low bid for each project, ensuring that the designated company would be awarded that contract. Such an arrangement is

a; illegal per se

b:illegal as judged under the rule of reason

c.legally justifiable due to economic conditions in the marketplace

d;legal under antitrust law since it does not fix prices