After operating for a month, Lochlan Mystrie's business completed the following transactions during the latter part of September:
Sep. 22 Performed service for clients on account, $6,000.
30 Received cash on account from clients, $4,500.
30 Received a telephone bill, $150, which will be paid during November.
30 Paid cash for advertising expense of $900.
30 Paid cash for monthly salary to his assistant, $3,900.
Journalize the business transactions. Include an explanation with each journal entry.