Total surface area of cuboid exclude one surface =2(lb+bh+lh)−lb ⇒ Total surface area of cuboid exclude one surface =2[(12×8)+(8×4)+(12×4)]−[12×8] ⇒ Total surface area of cuboid exclude one surface =352−96 ⇒ Total surface area of cuboid exclude one surface =256cm2 ⇒ Cost of painting =256×50= Rs. 12800 ∴ The cost of painting is Rs. 12,800 The correct option is 3 i.e. Rs. 12,800