Answer:
$100
Step-by-step explanation:
The maximum amount Alexander benefits is $250
Mary's cost due to the noise is $350
The difference between Alexander's benefit and Mary's cost due to inconvenience = $(350-250) = $100.
If Mary pays a legal fees of $100 to the lawyer , she will still have $250 to offer the maximum benefit to Alexander to reduce the noise .
She might still be able to negotiate a reduction in the payment made to Alexander and also make some gain.
Any attempt to pay more than $100 for legal fees means that the arrangement will not be beneficial to Mary if Alexander demands for the maximum benefit.