Total surface area of a cuboid = 2[(Length ×Breadth) + (Breadth ×Height) + (Height ×Length)]

Total surface area = 2[(40×30) + (30×20) + (20×40)] cm² = 2(1200+600+800) cm²

= 2(2600) cm² =5200 cm²

Lateral surface area of a cuboid = 2(Length +Breadth) ×Height

Lateral surface area = 2(40+30) × 20 cm² = 140× 20 cm²

= 2800 cm²