Answer:
Step-by-step explanation:
The specified set is fairly limited in size, so we can simply check all the choices and see which works:
For n ∈ {1, 2, 3, 4}
... 4n ∈ {4, 8, 12, 16}
Of these values, only the first three {4, 8 12} are less than 16. (16 is equal to 16, not less than 16.)
The corresponding values of n are {1, 2, 3}.