Final answer:
The formula for tax on labor income and interest income at rate tI is: Tax = Labor Income * tI + Interest Income * tI. option b.
Step-by-step explanation:
The correct formula for tax on labor income and interest income at rate tI is option B: Tax = Labor Income * tI + Interest Income * tI.
When calculating taxes on labor income and interest income, you need to multiply each income by the tax rate tI and sum the results. Multiplying labor income and interest income by the tax rate separately ensures that the tax amount is calculated correctly for each type of income. When calculating taxes on labor income and interest income, you need to multiply each income by the tax rate tI and sum the results.