Assume firm i and firm j have constant marginal cost = c for an identical good in an oligopolistic market. They compete to set prices Pi and Pj. They face a total market demand Q, where if Pi > Pj, the demand for firm i is 0. If Pi < Pj, the demand for firm i is Q. If Pi = Pj, then they share the market equally and hence the demand for firm i is Q/2. In equilibrium, the prices of firms i and j are
1
Pi > Pj = c
2
Pi > Pj > c
3
Pi < Pj < c
4
Pi = Pj = c