Total volume = Length × Breadth × Height. Then find \(\frac{9}{10}\) of it.<br><br>&bull; Total volume = 5 × 4 × 20 = 400 cm&sup3;<br>&bull; Volume of detergent = \(\frac{9}{10}\) × 400<br>&bull; 400 ÷ 10 = 40; 9 × 40 = 360 cm&sup3;<br><br>Final Answer: B: 360 cm&sup3;