The Payoff Matrix Below Shows the Payoffs for Firm a and Firm

The payoff matrix below shows the payoffs for Firm A and Firm B,each of whom can either "cooperate" or "cheat." The numbers in parentheses are (payoff for A,payoff for B) .
Firm B
Firm A TABLE 11-2
-Refer to Table 11-2.Of the choices provided below,what is the minimum value for x in order for both firms' cheating to be a Nash equilibrium?

A) 25
B) 40
C) 60
D) 70
E) 80