Answer
$\$ 171,793.82$
Work Step by Step
A sinking fund is an account earning compound interest into which you make periodic deposits. $\\$
$FV=PMT\displaystyle \cdot\frac{(1+i)^{n}-1}{i}\\\\$
Here, $\\$
$t=20$ years$,\\$
m= $4 \ \ \ $compounding periods per year,$\\$
$n=mt=80 \ \ $(total number of periods)$\\$
$\displaystyle \mathrm{i}=\frac{r}{m}=\frac{0.07}{4}=0.0175 \ \ $(rate per compounding period$)\\$
$PMT=1000\ \ \ $( payment at the end of each period)$\\\\$
$ FV=150\displaystyle \cdot\frac{(1+\frac{0.03}{12})^{240}-1}{\frac{0.03}{12}}\approx$171793.824243
