Answer:
The total number of combinations in which the movies can be rented such that there is at least one documentary is 27589.
Explanation:
The total movies are given as 19 mysteries +12 documentaries=19+12=31
Now the number of total combinations such that 4 movies are rented is given as

Now the number of total combinations with no documentary is given as

So the number of combination such that at least one movie is documentary is given as
=Total Combinations-Combinations with no documentary
=31465-3876
=27589
So the total number of combinations in which the movies can be rented such that there is at least one documentary is 27589.