Models & Qualitative Behavior · Hard problem

For the autonomous equation $y' = y(y - 2)^2(3 - y)$, let $a = \displaystyle\lim_{t\to\infty} y(t)$ for the solution with $y(0) = 1$, and $b = \displaystyle\lim_{t\to\infty} y(t)$ for the solution with $y(0) = 5$. Find $a + b$.