$(5$ points$)$ Solve the following DE$,$ using Variation of Parameters Method.

$y^{\text{'}\text{'}}-2y^{\text{'}}+y=\frac{e^t}{t^2+1}.$

Possible answers

a$.$

$lny=e^t[(c_1-\frac{1}{2}ln(t^2+1))+(c_2-arctan(t))]$

b$.$

$y=(c_1-\frac{1}{2}ln(t^2+1))+t(c_2-arctan(t))$

c$.$

$y=e^t[(c_1-\frac{1}{2}ln(t^2+1))+t(c_2-ta{n}^{-1}(t))]$

d$.$ None of the above