Let the dimensions be 4x,2x,x
Total surface area is equal to 2{(4x × 2x) + (2x × x ) + (4x × x )}
⇒ 2(8x² + 2x² + 4x²) = 2800 (given)
⇒ 14x² = 1400
⇒ x² = 1400/14
⇒ x² = 100
⇒ x = √100 = 10
volume = 4x × 2x × x = 8x³
= 8×(10)³
= 8000 m3