Question la: Find the point or the points on the surface xyz = 6 such that the tangent plane is parallel to the plane 1x + 2y + 3z = 0 Question 1b: Let z = f(x, y) be a function. Let I(s) be a smooth curve which parameterizes of the zero level of f. Can I self-intersect? If so, give an example. If not, explain why