```rstudio
library("dplyr") ## load
-TimeSum <- (TimeTracking %>% group_by(Category) %>% summarize(Duration = sum(Duration)))
-pie(TimeSum$Duration, TimeSum$Category
+TimeSum <- (TimeTracking %>% group_by(Category) %>% summarize(Duration = sum(Duration))))
+pie(TimeSum$Duration, TimeSum$Category)
```
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