John has been Mrs Yung's investment adviser for 30 years. The 84-year-old Mrs Yung has confidence in John's advice as her net worth had grown slowly if steadily through the years. In October 2018, she buys from John a structured financial product ("Pacific Prosperity Bonds") in which the payout dependson 8 formulas; the determination of which  formula applies depends on the USD-RMB exchange rate, the Purchasing Managers' (PMI) index, as well as the Dow Jones, Hang  Seng and  Shanghai  stock indices. In February 2019, MrsYung is diagnosed with senile dementia. When Tim, her nephew managing her affairs, discovers that she has invested 50% of her net worth in the 'bonds', he seeks to rescind the contract on her behalf. Advise Tim.