Mastering simple joins

Three new data.tables have been loaded into your R session containing information about the geography and population of Australia: area, capitals, and population. Your goal is to perform a sequence of joins to build a single data.table containing information about the geographical area of each Australian state and the population of its capital city, storing the final result in a new variable: australia_stats. There are three data.tables so you will need to perform two joins. First, you will join capitals and population, and then you will join the resulting data.table to the area.