A constant perpetuity with cash flow, $C,$ will have the first cash flow occur exactly $18$ years from now. Each subsequent cash flow will be exactly $9$ years after the prior cash flow. You have used the formula, $PV=\frac{C}{r}($correctly$)$ to determine a value. The determined value needs to be discounted exactly how many years to get the PV today of the cash flows?

The determined value needs to be discounted exactly $.....$years to get the PV today of the cash flows. Discount Rate isnt given.