i know the answer is Horizontal marketing system but why ... 4 to 5 sentence is enough to answer

In 2015, when Kmart needed to develop an efficient procurement and inventory system but could not afford to build one from the ground up, it turned to the grocery wholesaler Fleming. The two companies formed a $4.5 billion supply chain alliance governed by a joint team based in Kmart headquarters. Kmart expects the alliance will save $400 million during the first three years Identify and explain the channel dynamics implemented by Kmart and Fleming in this scenario?