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Assume that the fundamental relation for a 2-dimensional surface phase in a multi-component system is given by dU=TdS+dA+iidni where is the line tension and A is the total surface area. The Euler relation is given by U=TS+A+iini Derive the Gibbs-Duhem relation for a surface phase. (This equation is also known as the Gibbs adsorption equation.) (Hint: Look at the derivation of the Gibbs-Duhem equation as presented in class.)