For which interval is the function constant?
(4, ∞)
(0, 4)
(−4, 0)
(−∞, −4)

The interval from x = -4 to x = 0 is when the graph is completely flat. 

We can write this interval as -4 < x < 0 which becomes (-4,0) in interval notation

That's why the answer is choice C

Note: be careful not to mix up interval notation and ordered pair notation

n = 20

Step-by-step Explanation:
When dealing with ratios, there is always most likely a second number given to you. This number is going to be 1.
When looking for n, you have to look for all of the numbers, in this case there is only two.
1 is the hour, so now you just need the 20 minutes.
If the ratio is 1:n, this means that n would have to equal 20.
1:20