Concept:The cistern is open at the top, so the lead lining covers the bottom and the four side walls only.Explanation:Given: length =4.5 m, breadth =3 m, and capacity =50 m3.Height of cistern:h=4.5×350=27100≈3.704 mArea to be lined:Bottom area =4.5×3=13.5 m2Side walls area =2h(l+b)=2×3.704×(4.5+3)=55.56 m2Total lining area =13.5+55.56=69.06 m2Weight of lead required:=69.06×27=1864.62 kgAnswer:Option B: 1864.62 kg