︽ ︾
3. 150 400 2. 1000 1000 500 5 1. 250 30 (0.02~0.06 ) (0.004~0.006 ) 3. 300~500 5% 2000~4000 2~3 2. 5% 1000~2000 ) 6000~10000 1. 8% ~10% (
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