As you walk the aisles of a popular discount grocer - Trader Joe's two things (among others) strike most customers- almost everything is branded as a...

As you walk the aisles of a popular discount grocer - Trader Joe's two things (among others) strike most customers- almost everything is branded as a Trader Joe product (and TJ has no manufacturing facility anywhere) and that products similar to more expensive branded varieties are available at prices below what a branded product would cost at the super market. TJ strictly does not reveal who the suppliers are, but it has been long suspected that firms such as General Mills, Kraft Foods and Wonderful supply the same product to TJs as their branded variants in neutral packaging. Knowing what you know, why would  a. Firms supply the same product for sale at a lower price to Trader Joe's; b. What role is Trader Joe playing in the overall business strategy of these firms?