The document discusses the composition and phases of a lead-tin alloy at eutectic composition after the eutectic reaction. It determines that the alpha phase comprises 45% of the alloy and is 19% tin, while the beta phase comprises 55% of the alloy and is 97% tin. It then calculates that for 200g of alloy, the alpha phase mass is 90g and the beta phase mass is 110g. It further calculates the masses of lead and tin in each phase. The document also contains information about determining the phases and amounts of cementite, austenite, and alpha in a steel alloy.