The Colombo Company started operations this month and had the following transactions 1. Owners invested $15,000 to start the company 2. Borrowed $5,500 from a bank 3. Paid $2,000 for office rent 4. Purchased $250 of equipment on account 5. Sold $2,400 of services to customers on account 6. Paid $150 owed to suppliers from previous purchase 7. Paid payroll of $8,900 What is the company's total stockholder's equity at the end of the month?