Laplace Transform Question...

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I have this Laplace transform

$$B^*(s)=\frac{1-\frac{\mu }{\mu +s}}{s-\lambda +\frac{\lambda \mu }{\mu +s}}$$

and I am trying to compute the moments.

When I take the derivative and then evaluate it at $s=0$, it is not determinable. I.e.,

$$\frac{d}{ds}\left[\frac{1-\frac{\mu }{\mu +s}}{s-\lambda +\frac{\lambda \mu }{\mu +s}}\right]_{s=0} = \mbox{Indeterminate}$$

But, if I take the Inverse Laplace Transform, it exists...

$$[B^*(s)]^{-1}=e^{-t (\mu -\lambda )}$$

Question:

  1. How do you take the derivative of $B^*(s)$ and evaluate the result at $s=0$?