As per RBI guidelines, the mandatory age threshold for a minor to open and operate a Savings Account independently (without a guardian's joint signature) is:

A customer named Rajesh has a personal savings account with your bank. He also has a mandate to operate the account of his elderly aunt, Mrs. Sarita. Rajesh approaches the bank with a check drawn on Mrs. Sarita's account, signed by him as the mandate holder, payable to 'Self.' He explains that the money is needed for Mrs. Sarita's medical emergency. Simultaneously, the bank receives a letter from Mrs. Sarita's son claiming that the mandate given to Rajesh was revoked two days ago by Mrs. Sarita verbally. The bank has not received any written instruction from Mrs. Sarita. How should the bank handle this?

Which of the following is true about the authority to open and operate an account on behalf of another person?