Two newspapers $A$ 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 both $A$ and $B$ look into advertisements. Then the percentage of the population who look into advertisements is: