A 10 wt% aqueous solution of MgSO4 at 14.7 psia and 70°F is sent to a double-effect evaporator system with forward feed at a flow rate of 16,860 lb/h, to be concentrated to 30 wt% MgSO₄. The pressure in the second effect is 2.20 psia. The heating medium is saturated steam at 230°F. Estimated heat-transfer coefficients in Btu/h-ft2-°F are 400 for the first effect and 350 for the second. If the heat-transfer areas of the two effects are the same, and boiling-point elevations are neglected, determine: 

(a) Pressure in the first effect,
(b) Percent of the total evaporation occurring in the first effect,
(c) Heat-transfer area of each effect, and 

(d) Economy.