Answer and Explanation:
We will start from the point where the manager has three options over here we see that the payoffs for doing nothing is $110000, $160000 for subcontracting and $120000 for 2 machines bought, in this case subcontracting gives the best outcome of $160000.
Now if we move back on decision tree where two machines are bought and if demand is low then payoff is 0.2 * 80000 + 0.8 * 160000 for high demand = 16000 + 128000 = $144000.
Now if decide to buy only one machine then the payoff are 0.2 * 100000 + 0.8* 160000 (value for subcontracting)
= 20000 + 128000 = $148000
In case of event 1 we can see the benefits can be either $144000 or $148000 calculated above.
Se we see the best outcome is when the manager subcontracts and the benefit is $160000.
Best option is to buy no machines and the expected payoff is $160000.