The following transactions occurred during June: 6/1 Purchased two new maintenance carts on account at $750 each. Payment is due in 30 days. 6/8 Accepted $500 of advance payments from customers for services to be provided next month. 6/15 Received the utility bill for $300. Payment is due in 30 days. 6/20 Billed customers $1500 services provided. Payment is due in 30 days. 6/30 Received $500 from customers who were billed earlier What journal entry is necessary to record the collection on account from customers?