According to the problem
l=1.5m
b=1.25m
h=65cm =0.65m
Hence, the area of the sheet required for making the box = Area of the base + Lateral surface area of the box
=lb+2(bh+hl)
=(1.25)(1.25)+2{(1.25)(0.65)+(0.65)(1.5)}
=1.875+2{0.8125+0.975}
=1.875+2(1.7875)
=1.875+3.575
=5.45m2
(ii) Hence the cost of sheet =5.45×20=Rs.109