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 proprietorship..
2) Mark paid the first month's rent with $700.
3) Mark purchased equipment by paying $2,000 down and executing a note payable for $4,500.
4) Mark purchased supplies for $850 cash.
5) Mark billed a client for $4,000 of design services completed.
6) Mark received $3,000 of the account for the completed services.
What is the balance in Service revenue?

A) $1,000
B) $3,000
C) $4,000
D) $3,150