Final answer:
Under a proportional income tax, the tax revenue is calculated by multiplying the taxable income by the tax rate. The tax revenue raised when the tax rate is 10 percent is $4,000 for Ciara, $10,000 for Isabella, and $20,000 for Justin. When the tax rate is 15 percent, the tax revenue increases to $6,000 for Ciara, $15,000 for Isabella, and $30,000 for Justin.
Step-by-step explanation:
Under a proportional income tax, the tax revenue is calculated by multiplying the taxable income of an individual by the tax rate. In this case, if the tax rate is 10 percent, the tax revenue would be:
Tax revenue for Ciara = $40,000 x 0.10 = $4,000
Tax revenue for Isabella = $100,000 x 0.10 = $10,000
Tax revenue for Justin = $200,000 x 0.10 = $20,000
If the tax rate is increased to 15 percent, the tax revenue would be:
Tax revenue for Ciara = $40,000 x 0.15 = $6,000
Tax revenue for Isabella = $100,000 x 0.15 = $15,000
Tax revenue for Justin = $200,000 x 0.15 = $30,000