Answer:
All positive integers and zero
A is correct
Step-by-step explanation:
A box of pencils costs $10
The total cost (c) as a function of the number of boxes (b) is expressed as
c = f(b) = 10b
The function, f(b) = 10b
b is independent variable and c is dependent variable.
For any function find domain using independent variable.
b represents number of boxes.
Number of boxes neither be negative nor decimal.
Possible value of b: {0,1,2,3,4,5,.......}
All positive integers and zero.
Domain: All positive integers and zero