Measurement of big box, l = 25 cm.

b = 20 cm.

h = 5 cm.

∴ TSA of eacxh big box = 2(lb + bh + lh)

= 2 [25 × 20 + 20 × 5 + 25 × 5]

= 2 [500 + 100 + 120]

= 2 (725) T.S.A. =1450 cm^{2} .

For all the overlaps 5% of the total surface area is required extra.

\(\frac{5}{100} \times1450\)

= 72.5 cm^{2} .

∴ Total surface area of big box,

TSA = 1450 + 72.5 = 1522.5 cm^{2} .

Area required for 1 box is 1522.5 cm^{2}

Area required for 25 boxes … ?…

= 1522.5 × 250 = 380625 cm^{2} .

Dimension of small box, l = 15 cm. b = 12 cm. h = 5 cm.

∴ TSA of each small box = 2(lb + bh + lh)

= 2 [15 × 12 + 12 × 5 + 15 × 5]

= 2 [180 + 60 + 75] = 2 × 315

= 630 cm^{2} .

More area to overlap cardboard is 5% more.

For 100 cm^{2} , 5 cm^{2}

For 630 cm^{2} , …?… = 31.5 cm^{2} .

∴ T.S.A.= 630 + 31.5= 661.5 cm^{2} .

TSA required for 1 box is 661.5 cm^{2}

TSA required for 250 boxes …?… = 661.5 × 250 = 165375 cm^{2} .

∴ To prepare 500 boxes, TSA = 380625 + 165375 = 546000 cm^{2} .

Cost of 1000 sq.cm, of cardboard is Rs.4 Cost of 546000 sq.cm of cardboard is ?

= Rs. 2184