Given the following Laplace transforms \(F(s)\), find the function \(f(t)\). Note that in each case there are an infinite number of poles, resulting in an infinite series representation.

a. \(F(s)=\frac{1}{s^{2}\left(1+e^{-s}\right)}\).

b. \(F(s)=\frac{1}{s \sinh s}\).

c. \(F(s)=\frac{\sinh s}{s^{2} \cosh s}\).

d. \(F(s)=\frac{\sinh (\beta \sqrt{s} x)}{s \sinh (\beta \sqrt{s} L)}\).