2. Allen gave P50,000.00 to Marco who signed a receipt stating: "This is to acknowledge payment by Allen in the amount of P50,000.00." Allen later complains that she received nothing from Marco for the P50,000.00. Is Marco bound to return the P50,000.00?

3. In a contract stating "Sold to Analou for P500,000.00 a parcel of land belonging to Jacob in my hometown." Is the sale valid?

*Please also include what Article this case belongs based on Phillipine law of Obligation and Contracts