Imagine you have been tasked with determining a sampling plan for a survey for a retailer, using the retailer's CRM system as the source of the sampling frame. This survey is the last part of a multi-method study, and the retailer needs the results to be precise. The retailer knows that \\( 20 \\% \\) of its customers provide over \\( 80 \\% \\) of its revenues and is very interested in having them represented in the survey. Furthermore, the economic importance of those customers makes it imperative for the retailer to have precise estimates. What sort of sampling technique would you recommend (be specific for full credit) and why