Answer:
0 ≤ x ≤ 30, −3 is the answer.
Step-by-step explanation:
The domain of the function is all the x values between the highest and the lowest values of x.
The graph shows that the function starts at [tex]x=0[/tex] and ends at [tex]x=30[/tex]; and it is not defined for [tex]x>30[/tex] and [tex]x<0[/tex]; therefore the domain is
[tex]\boxed{0\leq x\leq 30.}[/tex]
The average rate of change of the function is the slope of the line that best approximates the function, and we see that a line from [tex](0,90)[/tex] to [tex](30,0)[/tex] best approximates the function, and its slope is:
[tex]\frac{90-0}{0-30} =-3[/tex]
Therefore the average slope is -3.
So the correct choice is the third one: [tex]0\leq x\leq 30, -3[/tex]