Is the answer D?

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Mandy enters a written agreement to rent a motor home for six days. Persons under age 25 are not permitted to drive it under terms of the written agreement. Mandy calls the rental company on the third day and asks if Dave, age 23, can drive it. The rental company says Dave can drive it if Mandy pays an extra $10 per day when he returns the motor home. When Dave drives in to return the motor home, the rental company refuses to return the $500 deposit because the written contract says any breach of the contract will result in the forfeiture of the entire damage deposit. Which is true? Mandy loses because of the parol evidence rule. Mandy loses because he had not yet paid the $10 extra per day. Mandy wins because the parol evidence does not apply. Mandy loses because of the Statute of Frauds