Julie has preferences for food, f, and clothing, c, described by a Cobb-Douglas utility function u(f,c) = f ·c. Her marginal utilities are MUf = c and MUc = f. Suppose that food costs $1 a unit and that clothing costs $2 a unit. Julie has $12 to spend on food and clothing.
What is the mathematical expression for sJulie's MRS in terms of f and c?