A developer is testing a new AI model integrated with an external calculator. The system is designed to trigger the calculator only when it encounters a mathematical expression enclosed in ≪...≫ that also contains an equals sign (=) to signal the end of the expression to be evaluated. The developer gives the model a word problem, and it generates three different potential responses. Evaluate each response below and explain why it would or would not successfully trigger the external calculator according to the specified rule.