Derive the lever rule for a general mixture of two phases, and . Let the composition of the alloy be C (wt\% of alloying element), the compositions of the phases be C and C, and the weight fractions of the phases be W and W. [Hints: find an expression conserving the mass of the alloying element between the alloy and the two phases, then define a,b and 1 in this notation, and use the overall conservation of mass expressed in W+W=1