Two newpapers A and B are published in a city. It is known that 25% of the city population reads A and 20% reads B while 8% reads both A and B. Further, 30% of those who read A but not B look into advertisements and 40% of those who read B but not A also look into advertisements while 50% of those who read A and B look into advertisements. Then the percentage of the population who look into advertisement is: