Answer:
The reasonable domain of f(x) based on the context:
0 ≤ x ≤ 40
Explanation:
The domain of a function is the collection of all the x-values where the function is defined.
We are given a modelling function f(x) which denotes the height f(x), in feet, of the food packet at different times x,in seconds by:

The independent variable i.e. x has to be greater than or equal to zero.
i.e. x ≥ 0
and also the value of function i.e. f(x) has to be greater than or equal to 0
( because the packet will either reach the ground i.e. f(x)=0 or will be at some level above the ground i.e. f(x)>0 )
Hence, we have:

Also, by the graph we have to check all those x where the function function is greater than equal to zero and also x≥0.
Hence, the domain of the function is:
0 ≤ x ≤ 40