Answer
$a.\qquad{{\$}} 3686.45$
$b.\qquad{{\$}} 3678.79$
Work Step by Step
$ a.\qquad$
Monthly compounding, $n=12$
$P=?$ (present value)
$A=10,000$
$t=20$
$r=0.05$
$P=A\displaystyle \cdot(1+\frac{r}{n})^{-nt} =10,000(1+\displaystyle \frac{0.05}{12})^{-12\cdot 20}\approx {{\$}} 3686.45$
$ b.\qquad$
Continuous compounding, $t=20,\ r=0.05$,
$P=Ae^{-rt}=10,000e^{-0.05\cdot 20}\approx{{\$}} 3678.79$
