Find the net present value $($NPV$)$ of the following cash flows when the discount rate is $7\%$ pa:

$$80,000$ in $3$ years $($t$=3)$;

$$90,000$ in $4\mathrm{.}5$ years $($t$=4\mathrm{.}5)$; and

$$100,000$ in $6$ years $($t$=6).$

The net present value of these payments is: