CDC Limited Buys Goods from and Sells Goods to DAD

CDC Limited buys goods from and sells goods to DAD Limited. CDC Limited owes DAD Limited £8,400, while DAD owes CDC Limited £12,600. The two companies agree to net off the amounts owed by each company to leave an amount owing by DAD Limited to CDC Limited of £4,200 (£12,600 - £8,400) . What is the correct double entry in the books of CDC Limited to record this netting off of £8,400 between the two companies?

A) Debit sales £8,400, Credit purchases £8,400.
B) Debit trade receivables control account £8,400, Credit trade payables control account £8,400
C) Debit purchases £8,400, Credit sales £8,400
D) Debit trade payables control account £8,400, Credit trade receivables control account £8,400.