\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
The following data shows the marks (out of 20) obtained by 9 students in a math exam:$$1,\;19,\;10,\;2,\;18,\;11,\;5,\;15,\;10$$Find the interquartile range of the marks.