A function $y(t)$ satisfies the differential equation

$\frac{dy}{dt}=y^4-9y^3+20y^2$

$(a)$ What are the constant solutions $of$ the equation? $(Enter$ your answers $as$ a comma$-$separated list.$)$

$y=$

$(b)$ For what values $ofyisy$ increasing? $(Enter$ your answer $in$ interval notation.$)$

yin

$(c)$ For what values $ofyisy$ decreasing? $(Enter$ your answer $in$ interval notation.$)$

yin