Show your work/reasoning. Be neat and orderly. Solve on scratch paper first. Simplify answers. 1. Let z = f(x, y) = cos (y-x). (a) (4 pts) Write the domain of f using set-builder notation. (b) (12 pts) Write the equations of the level curves of f for z= 0, 7/2, 7 . Solve for y in terms of x. (c) (12 pts) Sketch and label the level curves from part (b). 4 -3 -2 -1 0 3 -2 -3 2. Let z = f(x, y) = In . (a) (4 pts) Write the domain of f using set-builder notation. (b) (12 pts) Write the equations of the level curves of f for z=-2,0, 2 in standard form