Selamat tingal = good journey so is used like safe trip ...
Dada= an informal way of saying bye
Goodbye, in bahasa Indonesia:
"Selamat tinggal" ==> say the one who's leaving
"Selamat jalan" ==> say the one who leave behind ;)
Not accepting Selamat jalan, tuan is astonishing and a perfect example of what is wrong with this course.
The subtle difference between tinggal & jalan... whew! Never came up before & the course is almost finished!