In the case of ”satin” stitch, the under stitches should be half the length of the top stitches. This ensures that the top stitches cover the base fabric properly while creating a smooth, even surface. Satin stitch is often used for filling in shapes or areas in embroidery, and the technique requires precise control to prevent gaps between the stitches and to achieve a glossy, satin-like finish.
On the day of her examination, Riya sharpened her pencil from both ends as shown below. 
The diameter of the cylindrical and conical part of the pencil is 4.2 mm. If the height of each conical part is 2.8 mm and the length of the entire pencil is 105.6 mm, find the total surface area of the pencil.