Savings annuity calculator with graph help

Settings Remark
Periodic payment amount (PMT) The periodic payment amount is a stream of equal payments paid at the end of each payment period made at regular intervals over a specified period of time.

The amount may contain max two digits after its decimal point.
The amount entered may contain a comma (,) or point (.) as a decimal point separator.
Do not use the thousands separator in the amount.

Correct entered amounts
5123.04
5123,04
6123

Incorrect entered amounts
5,123.04
5.123,04
5123.041

The periodic payment amount (PMT) equation:
 PMT = FV * (R/N) and FV = N * T * PMT + I (1 + (R / N))N * T -1
where:
FV = Future value
I = Interest amount
R = Nominal interest rate per year (as a decimal, not in percentage)
T = Time period in years
N = Number of compounding periods in one year
PMT = Periodic payment amount, paid at the end of each payment period

Note:
A sinking fund is when we know the future value of the annuity and wish to calculate the periodic payment amount.