Here, inner radius (r) = 24/ 2 cm = 12 cm

Outer radius (R) = 28/ 2 cm = 14 cm, h = 35 cm

Volume of the wood used in the pipe = π(R^{2} – r^{2}) h

= 22/ 7 [(14)^{4} – (12)^{2}] × 35 cm^{3}

= 22/ 7 × 26 × 2 × 35 cm^{3} = 5720 cm^{3 }

Mass of 1 cm^{3} of wood = 0.6 g

∴ Mass of 5720 cm3 of wood = 0.6 × 5720 g = 3432 g **= 3.432 kg Ans.**