Answer:
2 layers, 3×2 cans per layer
Explanation:
Factors of 12: 1, 2, 3, 4, 6, 12
The box can have 1 layer of 12 cans, 2 layers of 6 cans each, or 3 layers of 4 cans each.
In each case below, the total surface area is 2(LW + LH + WH)
1 layer, 12×1 cans
L = 84 cm; W = 7 cm; H = 10 cm
SA = 2996 cm²
1 layer, 6×2 cans
L = 42 cm; W = 14 cm; H = 10 cm
SA = 2248 cm²
1 layer, 4×3 cans
L = 28 cm; W = 21 cm; H = 10 cm
SA = 2156 cm²
2 layers, 6×1 cans per layer
L = 42 cm; W = 7 cm; H = 20 cm
SA = 2548 cm²
2 layers, 3×2 cans per layer
L = 21 cm; W = 14 cm; H = 20 cm
SA = 1988 cm² <--------------- smallest surface area
3 layer, 4×1 cans per layer
L = 28 cm; W = 7 cm; H = 30 cm
SA = 2492 cm²
3 layers, 2×2 cans per layer
L = 14 cm; W = 14 cm; H = 30 cm
SA = 2072 cm²