I have a question about federal income tax.

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The question of sentence are

Recall from the SUA that corporate income tax rate bracket applicable to Waren for 2017 are: 15% of the first 50,000 of pre-tax income,

plus 25% of the next 25,000, plus 34% of the next 34,000, plus 39%of the next 235,000.

Is 15% of the first 50,000 of pre-tax income mean is individual annual person's salary?

There are three workers and I need to find feral income tax. I am assuming that 50,000 for

the first person( who makes less) and next person for 25%.

Could you explain this sentence, please?

Thanks.