Compute the net tax payable or refund due for Tim and Sarah Lawrence for 2018

I need help understanding how we get 8197.5 on the section where we do 17850 to146400 for 15%, and for the 3 lines after that...

Rate scheddies in your analySIS n Problem 48. Tim and Sarah Lawrence are married and file a joint return. Tim's Social Security number is 123-45-6789, and Sarah's Social Security number is 111-11-1111. They reside at 100 Olive Lane, Covington, LA 70434. They have two dependent children, Sean and Debra, ages 12 and 16, respectively. Sean's Social Security number is 123-45-6788, and Debra's Social Security number is 123-45-6787. Tim is a self-employed businessperson (sole proprietor of an unincorporated business), and Sarah is a corporate executive. Tim has the following income and expenses from his business. Gross income Business expenses $325,000 201,000 Records related to Sarah's employment provide the following information. Salary Unreimbursed travel expenses (including $200 of meals) $145,000 1,600 Other pertinent information for the tax year includes the following. Proceeds from sale of stock acquired on July 15, 2018 (cost of $12,000), and sold on August 1, 2018 Proceeds from sale of stock acquired on September 18, 2017 $9,800 (cost of $5,000), and sold on October 5, 2018 Wages paid to full-time domestic worker for housekeeping and 3,800 child supervision Interest income received Total itemized deductions (not including any potential deductions above) Federal income tax withheld Estimated payments of Federal income tax 10,000 7,000 27.900 31,850 20,000