Assume that the subscription fee for Class A is 1.5%, and the redemption fee is 1.5% within seven days and 0.5% after seven days. Custody fee and management fee are the same and can be ignored, so it is easy to calculate.
Generally, if you buy A through reasonable channels, you can get a 10% discount on the subscription fee, so the subscription fee becomes 0. 15%. Redeem within seven days 1.5%, accounting for 1.65%.
The cost of Class C within 7 days: 0.4%/365*7=0.0077% in 7 days, plus 1.5% redemption, obviously Class C is cost-effective.
The fixed cost of Class A for more than seven days is 0. 15%+0.5%=0.65%.
If the cost of Class C becomes 0.4% of the annual expenses, the time when the cost of Class C will exceed that of Class A is: 0.65%/0.4%= 1.625 years.
Under the assumed rate, if it is held for more than 1.625 years, it is a class A cost performance.
Therefore, it is cost-effective to hold Class B for more than 5 years, Class A for 3-5 years and Class C for less than 3 years.