Final answer:
The Sara Lee Company is using the (Option b) market test method to forecast sales for a new ice cream cake by placing it in Atlanta supermarkets for four months.
Step-by-step explanation:
The forecasting method used by the Sara Lee Company to forecast sales for a new ice cream cake is Market test. In this method, the product is placed in Atlanta supermarkets for a period of four months to observe and analyze its performance. By tracking sales data and customer feedback during this market test, Sara Lee can make accurate sales forecasts for the ice cream cake.