Lakeview Stores, Inc. borrows $5,000 each from Simple Credit Corporation, First United Bank, and Superior Products Corporation. Lakeview uses its present inventory and any thereafter acquired to secure the loans from Simple Credit and First United. Simple Credit perfects its interest on April 1, followed by First United on April 5. Lakeview buys new inventory on April 10 from Superior Products Corporation and signs a security agreement, giving Superior Products Corporation a purchase-money security interest in the new inventory. On the same day, Superior Products Corporation perfects its interest and notifies Simple Credit and First United. Lakeview takes possession of the new inventory on April 15. On April 20, Lakeview defaults on all of the loans. 

Whose security interest has priority?