Answer:
Option C
Explanation:
Volume of the beam=lbh $=9\times \frac{40}{100}\times \frac{20}{100}$$= \frac{72}{100}m^{3}$
The weight of the iron beam is given as $1 m^{3} = 50 kg$
$\therefore \frac{72}{100}m^{3}$$=\frac{72}{100}m^{3}$ $=\frac{72}{100}\times 50=36 kg$
