\(\text{Here's a bit of a derivation of the monthly payment}\\ \text{ignore months and years for a moment and just let $r$ be the periodic rate}\\ \text{$n$ will be the number of periods. Let $\alpha = (1+r)$}\\ \text{every period we take the principal, apply interest, and subtract a payment}\\ p(k+1) = \alpha p(k) -pmt,~p(0) = loan\\ \text{If you work through this you find that}\\ p(n) = \alpha^n loan - pmt \sum \limits_{k=0}^{n-1} \alpha^k = \alpha^n loan - pmt\dfrac{\alpha^n-1}{\alpha -1}\)
\(\text{We want $p(n)=0$ and we need to solve for $pmt$}\\ \alpha^n loan = pmt \dfrac{\alpha^n -1}{\alpha-1}\\ loan = pmt \dfrac{1-\alpha^{-n}}{\alpha -1}\\ pmt =loan \dfrac{(\alpha-1)}{1-\alpha^{-n}} = loan \dfrac{r}{1-(1+r)^{-n}}\)
\(\text{Here we plug in $loan=1600000,~n=360,~r=\dfrac{0.03}{12}=0.0025$}\\ pmt = \$1600000\dfrac{0.0025}{1-(1.0025)^{-360}} = \$6745.66\)
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