$2000k\frac{g}{h}$ of a solution of NaOH in a single effect evaporator is concentrated to $50\%.$ If the enthalpy of the feed is $50k\frac{j}{k}g$ and enthalpy of the product is $200k\frac{j}{k}g,$ and enthalpy of the saturated steam is $1000k\frac{j}{k}g$ and the latent heat of the water is $900k\frac{j}{k}g.$ find the steam economy.