Length (1) = 25 cm, Breadth (b) = 20 cm, Height (h) = 5 cm        

 ∵ The box is like a cuboid and total SURFACE area of a cuboid = 2(LB + bh + hl)                

Area of a box = 2([25 × 20) + (20 × 5) + (5 × 25)] cm2                 = 2[500 + 100 + 125] cm2                 = 2[725] cm2 = 1450 cm2        

 Total surface area of 250 boxes = 250 × 1450 cm2 = 362500 cm2      

   For smaller box:                 l = 15 cm, b = 12 cm, h = 5 cm          

Total surface area of a box = 2[lb + bh + hl]          

= 2[(15 × 12) + (12 × 5) + (5 × 15)] cm2          

= 2[180 + 60 + 75] cm2          

= 2[315] cm2 = 630 cm2          

⇒ Total surface area of 250 boxes = 250 × 630 cm2                

= 157500 cm2          

Now, total surface area of both kinds of boxes                

= 362500 cm2 + 157500 cm2                

= 5,20,000 cm2          

Area for overlaps = 5% of [ total surface area]                          

∴ Total area of the cardboard required = [Total area of 250 boxes] + [5% of total surface area]                

= 520000 cm2 + 26000 cm2                

= 546000 cm2                

Cost of cardboard:                

∵ Cost of 1000 cm2 = Rs. 4