Answer:
Alternatives Airport at X Airport at Y
Buy land at X 6 -14
Buy land at Y -21 12
Buy land at X and Y -15 -2
Do nothing 0 0
probability 0.55 0.45
Payoff if you buy land at X = (0.55 x 6) + (0.45 x -) = -3
Payoff if you buy land at Y = (0.55 x -21) + (0.45 x 12) = -6.15
Payoff if you buy land at X and Y = (0.55 x -15) + (0.45 x -2) = -9.15
Payoff for doing nothing = 0
The best option is simply doing nothing. The risks are too high, the potential losses are very large and the benefits are really low.