Answer:
Debit to Service Revenue of $10,500. 
Step-by-step explanation:
Jackson's closing entries should be:
December 31, 2019
Dr Service revenue 10,500
 Cr Income summary 10,500
Dr Income summary 5,500
 Cr Office Supplies Expense 600 
 Cr Rent Expense 3,000 
 Cr Insurance Expense 1,900
Dr Income summary 5,000
 Cr Retained earnings 5,000
Dr Retained earnings 2,000
 Cr Dividends 2,000