Answer: Most valuable customers or client.
Explanation: Marketing is a strategy, and it needs critical thinking and planning to achieve it's goal. Decisions and ideas are brought together to achieve a goal and a change in decision or policy will definitely affect the process of marketing and its potential customers.
James decision to make some changes, will affect the plans and strategy to make customers demands. He will need to identify his most valuable customers and understand how this decision will affect them.
The very first step is to identify is most valuable customers and how this decision will affect them.