The correct answer is:
a. A tip of a given percentage (such as a 20% tip) will be larger if calculated after tax than if calculated before tax.
When a tip is calculated based on the total amount after sales tax, it results in a larger tip compared to calculating it based on the pre-tax amount. For example, if the meal before tax costs $50 and the sales tax is $5, the total bill would be $55. A 20% tip applied to the total bill would be $11, whereas 20% of the pre-tax amount ($50) would only be a $10 tip.