examday

/TMUA

A television station telecasts three types of programs $X,Y$, and $Z$. A survey gives the following data on television viewing. Among the people interviewed $60\%$ watch program $X$, $50\%$ watch program $Y$, $50\%$ watch program $Z$, $30\%$ watch programs $X$ and $Y$, $20\%$ watch programs $Y$ and $Z$, $30\%$ watch programs $X$ and $Z$, while $10\%$ do not watch any television program. The percentage of people watching all the three programs $X,Y$, and $Z$ is