Let \( y(t) \) be the solution of the initial value problem
\[
\frac{d^2 y}{dt^2} + a \frac{dy}{dt} + b y = f(t), a > 0, b > 0, a \neq b, a^2 - 4b = 0,
\]
with initial conditions \( y(0) = 0 \), \( \frac{dy}{dt}(0) = 0 \), obtained by the method of Laplace transform. Then