Final answer:
The CFO and Peter are least likely to develop a marketing budget while preparing the master budget, which focuses more on the core financial operations like sales, cash, and production.
Step-by-step explanation:
Peter is helping the CFO develop the master budget, which is an integral part of a company's financial planning process. Out of the options provided, they are least likely to develop a marketing budget. The sales budget, cash budget, and production budget are directly related to financial planning and operations and are essential components of the master budget.
The marketing budget, while important, is often a subset of the sales budget or a separate component of the operational budget, not the master budget itself.