Annual interest repayment: 54000/3= 18000.
Annual interest rate:18000/50000×100% = 36%.
1991August 3, the Supreme People's Court issued "Several Opinions on People's Courts Handling Lending Cases", in which Article 6 stipulates that the interest rate of private lending may be appropriately higher than the bank's interest rate, and local people's courts may specifically grasp it according to the actual situation in the region, but the maximum shall not exceed four times (including the interest rate) of similar loans from banks. Beyond this limit, the excess interest will not be protected.