(a) Circle the equation that generates the surface shown below. 22 + y? + z? = 1 x = y? + z? x = +y 2 + 22 y? = 1 y = 2 x a 2 = 1 (b) Given f(x,y) = y +x2, sketch a well-labeled contour map for z, = -2,-1,0, 1