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Rubin owned a van that he leased to his friend, Bruno for his food delivery business in 2018. The duration of the lease was for 5 years with $15,000 annual rent. In 2020, Bruno's business was greatly impacted because of the COVID-19 pandemic as he lost a number of contracts to deliver food to his corporate clients based in the city. Bruno realised that he could not afford the annual rental payment for the van unless the situation changed. He discussed his business downturn and financial difficulties with Rubin. He also complained that Rubin did not disclose that the van had a faulty air conditioning system which spoiled some of his food items on the way to deliver them. Rubin denied Bruno's accusation, however promised to reduce the rental amount to $5,000 until the business condition improved. In 2021, Bruno secured a huge contract with a major public hospital for providing meals to their patients. Bruno's earnings from the business increased exponentially. Rubin demanded from Bruno that not only did he have to pay the full rental amount from 2021, but also the shortfall for the year of 2020 forgone by Rubin. Advise Bruno, with reference to the relevant legal principles, whether he must pay all the amounts claimed by Rubin.