已知开环最小相位系统的对数幅频特性如图4(a)所示。若对系统实施串联校正，校正环节的对数幅频特性如图4(b)所示。试根据图4回答： （1）该系统未校正前（图4(a)）的开环传递函数是什么？（10分）（2）校正环节（图4(b)）的传递函数是什么？（5分）（3）绘制系统校正后的对数幅频特性图。（10分）
Practice 3 The condition most helpful to spending appears to be price stability. If prices have been stable and people consider that they are reasonable, they are likely to buy. (1) Thus, it appears that the common business policy of maintaining stable p