NA in LR model summary(R)
You've given all four regions a dummy variable, so these are perfectly multicollinear, and the (unpenalized?) regression doesn't have a unique solution.  R automatically drops a column in this situation and reports the NA.

https://stats.stackexchange.com/q/212903/232706
https://stackoverflow.com/q/7337761/10495893
https://stats.stackexchange.com/q/25804/232706

(You can see where R calls C and subsequently FORTRAN functions, then inserts the NAs at
https://github.com/wch/r-source/blob/0f07757ad10ca31251b28a2c332812e63c0acf38/src/library/stats/R/lm.R#L117
A nice article that helped me find that: http://madrury.github.io/jekyll/update/statistics/2016/07/20/lm-in-R.html )