At the beginning of 2020 X company has following accounts in its statement of Financail Position: A/P $5000, Sales tax Payable $3000, Unearned Revenue $2500, N/P $6000, during January the company's sales on account was $8000 and paid $6000 from balance of A/P, at the entry of paying A/P, A/P should be?

a. Credited by $6000.

b. Debited by $8000.

c. Debited by $6000.

d. Credited by $8000.