The bee cannot see through the disc. So its line of sight to the origin must not intersect the graph of the function. If the bee's z-coordinate is less than 1 there is no problem: the bee can certainly see the flower. But if the bee's z-coordinate is greater than 1 then the disc may get in the way. Find the equation of the line from the bee's position to the origin and check where that line meets the plane z=1.