We can see that all the values of Φ1, Φ2 that are on the segment between (0, Θ1 + Θ2 − cs) and (Θ1 + Θ2 − cs, 0) in
Fig. 1 (right plot) are Nash equilibrium points (NE). In particular, if we assume that (x, y) is a point on this line segment and
u(x, y) is the corresponding payoff profile we have that for any h > 0