The Following Transactions Have Been Journalized and Posted to the Proper

The following transactions have been journalized and posted to the proper accounts.
1)Mark Call invested $7,000 cash in his new design services business.
2)The business paid the first month's rent with $700 cash.
3)The business purchased equipment by paying $2,000 down and executing a note payable for $4,500.
4)The business purchased supplies for $850 cash.
5)The business billed its clients a total of $4,000 for design services rendered.
6)The business collected $3,000 on account from one of its clients.
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What is the balance in Service revenue?
A) $1,000
B) $3,000
C) $4,000
D) $3,150