Derive the growing perpetuity formula. Begin with the formula of the $($infinite$)$ sum of discounted cash flows and multiply both sides by $((1+$r$)/(1+$g$))$ to ultimately simplify to the growing perpetuity formula. Annotate with $"$r$"$ as the discount rate, $"$g$"$ as the growth rate, and $"$C$"$ as the cash flow received per period.