You are asked to find the repayment amount of an annuity due (since the payments are at the beginning of each period) and we are given the present value of the annuity. Therefore we will use the present value of an annuity due formula 

$\displaystyle P=R(1+i)[ \frac{1-(1+i)^{-n}}{i} ]$

where $P$ is the present value, $R$ is the repayment per period, $i$ is the interest rate per period, and $n$ is the number of periods.

In our situation we have,

$P=\var{P}$,

$i=\frac{\var{ipa}\%}{\var{period[1]}}=\frac{\var{ipadec}}{\var{period[1]}}$, 

$n=\var{years}\times \var{period[1]}=\var{n}$, 

and therefore we have

$\displaystyle \var{P}=R (1+\frac{\var{ipadec}}{\var{period[1]}})[\frac{1-(1+\frac{\var{ipadec}}{\var{period[1]}})^{-\var{n}}}{\frac{\var{ipadec}}{\var{period[1]}}}]$

which we need to rearrange to solve for $R$.

Calculating this we find 

$\begin{align}R&\approx \var{C}\\&=\$\var{Crounded}\quad \text{(to the nearest cent)}\end{align}$