The dimensions of an oil tin are 26 cm × 26 cm × 45 cm.

Dimensions of the oil tin are $26 \mathrm{~cm} \times 26 \mathrm{~cm} \times 45 \mathrm{~cm} .$

So, the area of tin sheet required to make one tin $=2 \times($ length $\times$ breadth $+$ breadth $\times$ height $+$ length $\times$ height $)$

$=2 \times(26 \times 26+26 \times 45+26 \times 45)$

$=2 \times(676+1170+1170)=6032 \mathrm{~cm}^{2}$

Now, area of the tin sheet required to make 20 such tin $s=20 \times$ surface area of one tin

$=20 \times 6032$

$=120640 \mathrm{~cm}^{2}$

It can be observed that $120640 \mathrm{~cm}^{2}=120640 \times 1 \mathrm{~cm} \times 1 \mathrm{~cm}$

$=120640 \times \frac{1}{100} \mathrm{~m} \times \frac{1}{100} \mathrm{~m} \quad(\because 100 \mathrm{~cm}=1 \mathrm{~m})$

$=12.0640 \mathrm{~m}^{2}$

Also, it is given that the cost of $1 \mathrm{~m}^{2}$ of tin sheet $=$ Rs 10

$\therefore$ The cost of $12.0640 \mathrm{~m}^{2}$ of tin sheet $=12.0640 \times 10=$ Rs $120.6$