Very Simple Loan Calculator

It is a simple and convenient loan calculator that displays all on one screen without moving the screen.
If there are suggestions or bugs, please let me know by comment.

The functions provided are as follows.
1. Calculate two type payment method
- fixed amount
- fixed principal
- fixed interest
2. Display the payment schedule table
3. Calculation of the secondary sum, monthly average interest, monthly average repayment principal

very simple loan calculator!!