Answer:
Debit to Service Revenue of $10,500.
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