Duopoly

本来对Nash Equitlibrium 就不是非常清楚，刚碰到一道题，让后对这概念更模糊了，大家有空帮忙解释下duopoly和Nash equilibrium是什么关系啊，好像从来没看过这概念。谢谢！

Assume that two firms in a duopoly enter into a collusive agreement in an attempt to form a cartel
and restrict output, raise prices, and increase profits. According to the Nash equilibrium, a low price
is most likely charged by:
A. only one firm.
B. both firms.
C. neither firm.
Answer = C
The market outcomes for two firms in a
duopoly is shown in the diagram to the
right.
The lower left hand quadrant is the Nash
solution when there is no collusion.
However, with collusion, if ArcCo
shares at least enough of its profit in the
bottom right quadrant to provide BatCo
more than it would receive in the lower
left, it will be the optimal solution for the
pair: themaximum joint profits will arise
where both firms charge high prices
for the product.

是MOCK 的题，看了同晕，题目没给更多的条件，怎么就能画出右边的表格呢。做的时候直接选了A，囧。