Can you please explain how to do these I cannot figure it out

Imagine that a new tax law permits taxpayers to choose between taking an itemized deduction for cash charitable contributions or claiming a nonrefundable tax credit for the first $1,000 of cash charitable contributions (with the excess contributions nondeductible and no carryback or forward of excess amounts). For example, a taxpayer who gives $3,000 to charity may choose between claiming a $3,000 itemized deduction or a $1,000 credit. In each of the following situations, advise the taxpayer whether they should claim the itemized deduction or the new credit for charitable contributions and support your answer with calculations). Each taxpayer is single. Use 2019 tax rates and other tax law, as found in your textbook, to answer this question. Taxpayer A gave $6,000 to charity. This taxpayer has $90,000 AGI and no other itemized deductions besides the charitable contribution. Taxpayer B gave $4,000 to charity. This taxpayer has $200,000 AGI and other itemized deductions of $14,000. Taxpayer C gave $5,000 to charity. This taxpayer has $120,000 AGI and other itemized deductions of $11,000