Economy of evaporators used for concentrating sugarcane juice is

1. $\frac{kg\:of\:concentrated\:juice\:produced}{kg\:of\:steam\:supplied}$
2. $\frac{kg\:of\:steam\:supplied}{kg\:of\:sugarcane\:juice\:fed}$
3. $\frac{kg\:of\:water\:vaporized}{kg\:of\:steam\:supplied}$
4. $\frac{kg\:of\:sugarcane\:juice\:fed}{kg\:of\:water\:vaporized}$