Final answer:
Quantitative forecasting should be used when the situation is 'stable' and historical data exists.
Step-by-step explanation:
The forecasting method that should be used when the situation is 'stable' and historical data exists is Quantitative.
Quantitative forecasting involves using numerical data to make predictions and forecasts. It is based on historical patterns and trends in the data to forecast future outcomes.
For example, if a company wants to forecast future sales based on past sales data, they would use quantitative forecasting methods to analyze the historical data and make predictions.