Creating Loan Payment Calculation in Adobe Form

I'm in the process of creating a loan payment calculator within a form and looking to automate the calcuations.

The way we complete the calculation is original payment amount multiplied by orginal frequency, then divide that value by the new frequency.

So - original payment of $200 with a biweekly frequency that is being changed to weekly would be calculated as:

200 x 26 = 5200

5200 / 52 = 100 for the new payment

There would be four fields involved:

Field #1 - Original Payment Amount

- data is automatically inputted from system

Field #2 - Original Payment Frequency

- data is automatically inputted from system

Field #3 - Payment Frequency

- front end user would select one of the following frequencies:

1. Monthly

2. Biweekly

3. Accelerated Biweekly (this calculation is the monthly amt divided by 2)

4. Twice Monthly

5. Weekly

Field #4 - New Payment Amount

- value of calculation would populate in this field

I'm having a difficult time trying to figure out how this can be inputted as it's very complex.

Thank you!