The formula for the lateral surface area of a cone—that’s the surface that isn’t the base—is π × r × sqrt(h² + r²); h is the height of the cone and r is the radius of its base. A circular #2 pencil is 6 mm in diameter, and a pencil sharpener creates a cone-shaped end that is 20 mm in height. Find the surface area of the sharpened part of the pencil.