In a LAN there are $100$ systems available. Some of these systems are having addresses in the form of $10\mathrm{.}0\mathrm{.}0.$x and the rest are having IPs in the form of $192\mathrm{.}168\mathrm{.}0.$x where x can be $0$ to $255.$ One public IP cost Rs $2000$ per year. How much amount needs to be allocated in a year so that all $100$ systems get access to Internet with minimal cost and approach to be followed.