Given the following tasks in an internet business setting, determine which forecasting technique is most suitable for each:
- Task I: Estimating next month's website traffic based on historical traffic data.
- Task II: Predicting whether a new email campaign will lead to an increase in subscriber engagement.
- Task III: Forecasting yearly sales trends based on multi-year sales data, considering seasonal variations.
- Task IV: Determining the impact of customer demographics on purchasing behavior.
Match each task with the appropriate forecasting technique.