please provide a reasoning outline, as it best helps to organize the narrative:

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

Whose security interest has priority?