Box A
Surface Area = sum of the areas of the individual boxes
Surface Area A = 2 ( 3 x 3 ) + 3 ( 2 x 3) + 1 (2 × 2) = 18 + 18 + 4 = 40 sq.cm
Surfaca Area B
= 2 ( 3x 6) + 2 ( 1 x 6) + 2 ( 1 x 3) = 36 + 12 + 6 = 54 sq.cm
Surface Area C = 6 ( 3x 3) = 54 sq cm.
Box A has the least surface area.