Function calculate_principal_from_amortization_payment

calculate_principal_from_amortization_payment(
    payment: number,
    apr: number,
    months: number,
    digits?: number,
): number
Calculates the initial principal balance given the payment amount, the interest rate, and the number of months of the loan
Parameters
- payment: number
  the monthly payment amount on the loan
- apr: number
  the interest rate of the loan
- months: number
  the number of months for the loan
- digits: number = 2
  the number of digits to round the result to
Returns number