Answer:
d. Winston pays Chloe once (as a fine) and refrains from playing music loudly.
Step-by-step explanation:
Coase Theorem states that in case of externalities : two parties can bargain and arrive at an efficient outcome, if the transaction costs are low.
Winston's loud music is a negative externality for neighbour Chloe. So, the negative external cost can be compensated , by including it in monetary exchange mechanism .
For negative external effect upto now : Winston should pay chloe 'fine', as the former's act has had an extra extra social cost on the latter . Winston should also refrain from paying loud music thereafter.