(2) when x= 1, y reading =, y will be = 20+0.4 = 20.4;

(3) As can be seen from the image, when 0; Y reading, so choosing a reading card is cost-effective;

? When x= 100, there is no difference between card reading and membership card;

When x> 100, y reads > y wishes, the membership card is cost-effective.