Total volume = Edge³. Initial water + tap water added.
• Total capacity = 21 × 21 × 21 = 9261 cm³
• Initial water = \(\frac{1}{3}\) × 9261 = 3087 cm³
• Tap adds 1.5 l/min for 3 min = 4.5 l = 4500 cm³
• Total water = 3087 + 4500 = 7587 cm³
• 7587 ÷ 1000 = 7 remainder 587
• 7 l 587 ml
Final Answer: 7 l 587 ml