Use traces to sketch the surface. (If an answer does not exist, enter DNE. Select Update Graph to see your response plotted on the screen. Select the Submit button to grade your response.) x2 + 4y2 z2 = 4 (Write an equation for the cross section at z = 0 using x and y.) $$ Correct: Your answer is correct. (Write an equation for the cross section at y = 2 using x and z.) $$ Incorrect: Your answer is incorrect. (Write an equation for the cross section at y = 0 using x and z.) $$ Incorrect: Your answer is incorrect. (Write an equation for the cross section at y = 2 using x and z.) $$ Incorrect: Your answer is incorrect. (Write an equation for the cross section at x = 0 using y and z.)