2. (a) Explain what the term 'zero-sum game' means.
Two teams, A and B , are to face each other as part of a quiz.
There will be several rounds to the quiz with 10 points available in each round.
For each round, the two teams will each choose a team member and these two people will compete against each other until all 10 points have been awarded. The number of points that Team A can expect to gain in each round is shown in the table below.
| \cline { 3 - 5 }
\multicolumn{2}{c|}{} | Team B |
| \cline { 3 - 5 }
\multicolumn{2}{c|}{} | Paul | Qaasim | Rashid |
| \multirow{3}{*}{Team A} | Mischa | 5 | 6 | 3 |
| \cline { 2 - 5 } | Noel | 4 | 1 | 7 |
| \cline { 2 - 5 } | Olive | 4 | 5 | 8 |
The teams are each trying to maximise their number of points.
(b) State the number of points that Team B will expect to gain each round if Team A chooses Noel and Team B chooses Rashid.
(c) Explain why subtracting 5 from each value in the table will model this situation as a zero-sum game.
(d) (i) Find the play-safe strategies for the zero-sum game.
(ii) Explain how you know that the game is not stable.
At the last minute, Olive becomes unavailable for selection by Team A.
Team A decides to choose its player for each round so that the probability of choosing Mischa is \(p\) and the probability of choosing Noel is \(1 - p\).
(e) Use a graphical method to find the optimal value of \(p\) for Team A and hence find the best strategy for Team A.
For this value of \(p\),
(f) (i) find the expected number of points awarded, per round, to Team A,
(ii) find the expected number of points awarded, per round, to Team B.