For river flow rate R(t) (in cubic meters per second), measured over 0≤t≤8 hours, the derivative is given by
R′(t)=t+2(t−1)(t−5).
Identify the interval(s) in 0≤t≤8 where the flow rate is increasing and the interval(s) where it is decreasing, justifying your answer using the sign of R′(t).