Chuck a single taxpayer earns $75,000 in taxable income and $10,000 in interest from an investment in city of Heflin bonds. Per the US Tax rate

Chuck a single taxpayer earns $75,000 in taxable income and $10,000 in interest from an investment in city of Heflin bonds. Per the US Tax rate schedule, how much federal tax will he owe? What is his average tax rate? What is his effective tax rate?What is his current marginal tax rate? 

The answer provided is he owes 14,931.25 in federal tax.  14,931.25= $4,681.25+25% (75,000 - 34,000)

How did they arrive at $4,681.25?  

Why is the parentheses (75,000-34,000). Where did 34,000 come from?