PURCHASE DISCOUNTS INVENTORY NET METHOD

Please explain the following transactions for periodic and perpetcual Discounts using the Net Method.

Receipt of Invoice Periodic Dr. Purchases 980 Cr. Accounts Payable 980 Perpetual Dr. Inventory 980 Cr. Accounts Payable 980 Payment within discount period Periodic Dr. Accounts Payable 980 Cr. Cash 980 Perpetual Dr. Inventory 980 Cr. Cash 980 Payment after discount period Periodic Dr. Accounts Payable 980 Dr. Interest Expense 20 Cr. Cash 1000 Perpetual Dr. Accounts Payable 980 Cr. Interest Expense 20 Cr. Cash 1000