Consider the nonhomogeneous equation.

$y^{\text{'}\text{'}}+6y^{\text{'}}+9y=(2t+t^4)e^{-3t}.$

By the method of undetermined coefficients, there is a solution to the equation which is of the form $y=Q(t)e^{-3t}$ where $Q(t)$ is a polynomial. The degree of $Q(t)$ is :

Select one:

a$.6$

b$.4$

c$.8$

d$.2$