说明：  某学校对教师每月工资的计算规定如下：固定工资＋课时补贴。教授的固定工资为5000元，每个课时补贴50元；副教授的固定工资为3000元，每个课时补贴30元；讲师的固定工资为2000元，每个课时补贴20元。定义教师抽象类，派生不同职称的教师类，编写程序求若干个教师的月工资。
(Monthly wages of teachers in a school of calculation are as follows: a fixed wage+ hours subsidies. Professor fixed wage of 5000 yuan, 50 yuan subsidy for each class an associate professor of the fixed wage is 3,000 yuan, 30 yuan subsidy for each class lecturer at a fixed wage is 2,000 yuan, 20 yuan subsidy for each class. Define abstract class teachers, derived the title of teachers of different classes, write a program seeking a number of teacher' s monthly salary.)