Andrew is the owner of a scallop boat. In 2015, Andrew leased the vessel to his friend, Steve, for 10 years as an annual rental of $10,000. In 2017, it became apparent that scallop numbers were declining and Steve soon realised that he would be unable to meet the annual rental charge unless the catch is improved. He approached Andrew and advised him of his fishing and financial difficulties. He also complained that the engine in the scallop boat was not as powerful as he had been led to believe. Andrew denied that he had ever made any promises or statements about the engine power. However, he said that he was prepared to halve the annual rental until the catch improved and, accordingly, the rental charge was reduced to $5,000.

In 2020, the catch improved to such an extent that Steve is able to resume paying $10,000 a year. Andrew was delighted and advised Steve that not only did he have to pay $10,000 a year until 2025, but also the $15,000 forgone by Andrew in the previous three years.

Advise Steve whether he must pay the $15,000 claimed by Andrew.

answer must be in IRAC style