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A drainage basin of 180 hectares comprises 40% wooded area, 45% grassed area and 15% paved area. Runoff coefficients for wooded, grassed and paved areas are 0.01, 0.2 and 0.95 respectively. The composite runoff coefficient for the drainage basin is ___________
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- 2 to 25
- 2.5
- 0.02 to 0.025
- 0.20 to 0.25