What will be the percentage increase in the area of the cube's surface if each of the cube's edges grows by 10%?	Choose the correct option.
A) 25 %  B) 28 %  C) 21 %  D) 30 %  E) 32 %

Rationale: "the question is very easy . my logic is the following : a surface = 6 * a ^ 2 after 10 % increase a surface = 6 * ( ( 1.1 a ) ^ 2 ) = 6 * 1.21 * a ^ 2 the increase in the surface area = ( 6 * 1.21 * a ^ 2 - 6 * a ^ 2 ) / 6 * a ^ 2 = ( 6 * a ^ 2 ( 1.21 - 1 ) ) / ( 6 * a ^ 2 ) = 1.21 - 1 = 0.21 = 21 % answer : c"
Answer: C