3. Use the Cobb-Douglas production function and costs below to answer questions that follow. y=f(,k)C=k(1)=w+rk (a) Use the equation for costs, C, above to derive an expression for isocost lines. (b) Use your answer from 3a and the production function above to diagram isoquants and isocost lines and the firm's optimal choice of inputs, and k. (c) Write down an equation that describes the firm's optimal choice from part 3b. (d) Is this optimal choice made by the firm profit-maximizing or cost-minimizing? In the long-run, are these choices ultimately different from one another? Briefly explain