The winner of a lottery receives $m$ dollars at the end of each year for $N$ years. The present value (PV) of this prize in today's dollars is $\mathrm{PV}=\sum_{i=1}^{N} m(1+r)^{-i},$ where $r$ is the interest rate. Calculate PV if $m=\$ 50,000, r=0.06,$ and $N=20 .$ What is $\mathrm{PV}$ if $N=\infty ?$