The reflector of a flashlight is in the shape of a parabolic surface. The reflections of all rays from the light bulb to any point on the parabolic surface will all be parallel to each other. The casting has a diameter of 16 centimeters and a depth of 8 centimeters. Find the focus to determine how far the light bulb should be placed from the vertex.(1 point) The light bulb should be placed how many centimeter(s) from the vertex.