The mean thickness and variance of silicon steel laminations are 0.2 mm and 0.02 respectively. The varnish insulation is applied on both the sides of the laminations. The mean thickness of one side insulation and its variance are 0.1 mm and 0.01 respectively. If the transformer core is made using 100 such varnish coated laminations, the mean thickness and variance of the core respectively are

• A. 30 mm and 0.22
• B. 30 mm and 2.44
• C. 40 mm and 2.44
• D. 40 mm and 0.24