Lenny D. answered 12/02/19
Former Tufts Economics Professor and Wall Street Economist
I think you have a problem with your Payoff Matrix
Firm 2
No Rebate Rebate
No Rebate 1 = 200 1= 120
2 = 120 2=160
Rebate 1= 220 1= 160
2= 40 2=140
It is bizarre that if both firms rebate that profits for firm 2 go up and firm 1 go down,. so be it.. Lets look at firm 2. If they opt for a rebate they will make either 160 or 140 depending upon what firm 1 does. if they do not rebate they make either 120 or 40. So for firm 2 the worst case scenario of a rebate is better than the best case scenario for no rebate.
Rebating is the dominant strategy for firm 2.
With firm 1 the worst case scenario with no rebate is 120 and the worst case with a rebate is 160. They do not have a dominant strategy but the max min strategy (best worst case is to rebate which happens to be the Nash equilibrium.
Hope this helps.