An evaporator working at atmospheric pressure is to concentrate a solution from $5\%$ to $20\%$ solids at the rate of $10000I\frac{b}{h}.$ The solution which has specific heat of $1\mathrm{.}0$ is fed to the evaporator at $20F$ and boils at $105F.$ Dry saturated steam at $20g$ is fed to the calandria, and the condensate leaves at the temperature of the condensing steam. If the heat transfer coefficient is $4000Bt\frac{u}{f}{t}^2.h.F.$ What is the required area of heat transfer surface and how much steam is required? The latent heat of vaporization of the solution may be taken as same as that of water.