Question

Let t be time in seconds and let r(t) be the rate, in gallons per second, that water enters a reservoir : r(t) = 600-30t
If the domain of r(t) is 0 <_t <_ 30, what is the range of r(t)?

Answer 1

since the function is linear, the range is the interval [r(0),r(30)]

Answer 2

or rather, since r is decreasing, [r(30),r(0)]
Question: does the water ever flow out? That is, can r(t) be negative? If not, then you have to truncate the range when r(t) = 0.