Steam balance unknown flows

The steam flows for a plant are shown in Fig. P5.21. Write the material and energy balances for the system and calculate the unknown quantities in the diagram (A to F). There are two main levels of steam flow 600 psig and 50 psig. Use the steam tables for the enthalpies. 

Consider, for example, a triple-effect evaporator. There are seven equations which may be written an enthalpy balance for each effect, a capacity equation for each effect, and the known total evaporation, or the difference between the thin- and thick-liquor rates. If the amount of heating surface in each effect is assumed to be the same, there are seven unknowns in these equations (1) the rate of steam flow to the first effect, (2) to (4) the rate of flow from each effect, (5) the boiling temperature in the first effect, (6) the boiling temperature in the second effect, and (7) the heating surface per effect. It is possible to solve these equations for the seven unknowns, but the method is tedious and involved. Another method of calculation is as follows ... 

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