https://zh.apacode.com/post/which-of-the-following-is-an-appropriate-time-to-exercise-the-redemption-right-of-the-redeemable-preference-shares-a-when-the-market-interest-rate-falls-b-when-the-company-has-sufficient-funds-and-there-is-no-other-purpose-c-when-the-company-does-not-want-to-be-restricted-by-the-agreed-terms-of-the-preferred-shares