The following transactions have been journalized and posted to the proper accounts. March is the first month of business operations for the sole proprietorship. Mar. 1 The business received $7000 cash from the owner in exchange for capital. Mar. 2 Paid the first month's rent of $800. Mar. 3 Purchased equipment by paying $3000 cash and executing a note payable for $4000. Mar. 4 Purchased office supplies for $750 cash. Mar. 5 Billed a client for $12,000 of design services completed. Mar. 6 Received $6000 on account for the services previously recorded. What is the ending balance in the Service Revenue account? $12,000 $7000 O $6000 $13,000