How we derive calculations to come up with the answer which is $13,500

The changes in account balances of the Dunedin Corporation during 2014 are presented below: Increase Assets $133,500 Liabilities 40,500 Common Stock 90,000 Additional Paid-In Capita. 9,000 Assuming there are no changes in retained earnings except for net income and a dividend payment of $19,500, the net income for 2014 should be $13,500