1、In an insurance company, each policy has a paper record or an electric record, or both of them. 60 percent of the policies having incorrect paper record have incorrect electric record and 75 percent of the policies having incorrect electric record have incorrect paper record. 3 percent of all the policies have both incorrect paper and incorrect electric records. If we randomly pick out one policy, what is the probability that it is one having both correct paper and correct electric record?
2、If for all x, x^2+ax+b = (x+c)^2, then a =?
（1）b=0；
（2）c=-3；
3、随机抽样10个产品有N个坏的，N<5，问N=？
（1）任取两个产品，都是坏的可能性为1/15；
（2）任取两个产品，一好一坏的可能性为7/15；
4、xyz<>0, 问x(y+z)>0?
（1）|x+y|=|x|+|y|
（2）|y+z|=|y|+|z|ffice ffice" />
5、1/a+1/b+1/c+1/d+1/e=1，a…e全是不同的正整数，问：a+b+c+d+e的least possible value？ | 
