The data set $\left[10,20,25,30,35,40,45,50,55,60\right]$ has median $Q_2=37.5$, first quartile $Q_1=25$, and third quartile $Q_3=50$. An outlier in a data set is a value that is more than $1.5$ times the interquartile range below the first quartile ($Q_1$) or more than $1.5$ times the interquartile range above the third quartile ($Q_3$), where the interquartile range is defined as $Q_3-Q_1$. How many outliers does this data set have?