Which one is correct. Can u expalin it in details?

A country has a current account balance of -$30bn and a capital and financial account balance (excluding official transactions by the central bank) of +$40bn. Assuming there are no errors and omissions in the balance of payments accounts, the central bank of this country must have purchased $10bn worth of its own currency on the foreign exchange market, and made additions to foreign currency reserves used $ 10bn of foreign exchange reserves to make sales of its own currency on the foreign exchange market used $ 10bn of foreign exchange reserves to make purchases of its own currency on the foreign exchange market sold $10bn worth of its own currency on the foreign exchange market, and made additions to foreign currency reserves