When non-metals combine with oxygen, they typically form acidic oxides. These oxides are also known as non-metallic or acidic anhydrides. The resulting compounds, when dissolved in water, produce acidic solutions. The acidic nature arises because non-metal oxides tend to react with water to form acids.
For example:
Carbon Dioxide (CO₂): \(3CO_2+H_2O→H_2CO_3\)
Carbon dioxide dissolves in water to form carbonic acid.
Sulfur Dioxide (SO₂): \(3SO_2+H_2O→H_2SO_3\)
Sulfur dioxide dissolves in water to form sulfurous acid.
Nitrogen Dioxide (NO₂): \(2NO_2+H_2O→2HNO_3\)
Nitrogen dioxide dissolves in water to form nitric acid.
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.
