P$$rchase$-$related transactions

The Stationery Company purchased merchandise on account from a supplier for $$8,900,$ terms $\frac{2}{10},\frac{n}{30}.$ The Stationery Company returned merchandise with an invoice amount of $$1,200$ and received full credit.

a$.$ If The Stationery Company pays the invoice within the discount period, what is the amount of cash required for the payment?

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b$.$ Under a perpetual inventory system, what account is gredited by The Stationery Company to record the return?