The oxygen obtained from 72 kg of water is

2H₂​O ⟶ 2H₂ ​+ O₂​

From above reaction, 2 moles of water produce 1 mole of O₂​

2 moles of water → 1 mole of O₂​

2 × 18 g water → 1 × 32 g O₂​

36 g water →32 g O₂​

72000 g water → ? (x) O2​  

⟹ x = $\frac{32\times \left(72000\right)}{36}$​

⟹x = 64000 grams

 = 64 kg

It produces 64 kg oxygen.