An aqueous solution contains $40\%$ Na$2$SO$4.$ Two streams are obtained from the crystallizer: a$.$ Na$2$SO$4*2$H$2$O crystals accompanied with a residual remaining solution and b$.$ Rest of the remaining solution. The outlet stream of the crystallizer contains $200$ g crystals$/100$ g of solution. These crystals are going to be dried, to obtain a dry product $($but not hydration water$),$ the residual liquid from the evaporator contains $80\%$ Na$2$SO$4.$

Determine:

a$.$ Ratio of grams of dry crystals$/$grams of original solution fed.

b$.$ Evaporated water.

NOTE: the solubility of the remaining liquid is $15$ g Na$2$SO$4/100$ g H$2$O P$.$M$.$ Na$2$SO$4=142$