In a certain city only two newspapers A and B are published, it is known that `25%` of the city population reads A and `20%` reads B, while `8%` reads both A and B. It is also known that 30% of those who read A but not B look int advertisements and 40% of those who read B bu not A look into advertisements while 50% of those who read both A and B look into advertisements What is the percentage of the population reads an advertisement? [1984]