Final answer:
Louise's employer should withhold $207.50 for federal income tax, based on the wage bracket method.
Step-by-step explanation:
Louise's employer should withhold $207.50 for federal income tax.
To calculate the amount, we can use the wage bracket method. First, we determine Louise's taxable income, which is $1,250 x 2 (since she is paid semi-monthly) = $2,500.
Next, we look at the wage bracket table for a single taxpayer with 3 withholding allowances on the pre-2020 Form W-4. Based on the table, for a taxable income of $2,500, the amount to withhold is $207.50.