Rui's utility function is U = X + 25XZ+Z. Let the price of good X be px, the price of good Z be normalized to $1.00, and U be her level of well-being. What is her expenditure function? Rui's expenditure function (E) is E = (Properly format your expression using the tools in the palette. Hover over tools to see keyboard shortcuts. E.g., a subscript can be created with the _ character.)