If $ f(t) $ is continuous for $ t \ge 0 $, the Laplace transform of $ f $ is the function $ F $ defined by
$$ F(s) = \int_0^\infty f(t) e^{-st}\ dt $$
and the domain of $ F $ is the set consisting of all numbers s for which the integral converges. Find the Laplace transforms of the following functions.
(a) $ f(t) = 1 $ (b) $ f(t) = e^t $ (c) $ f(t) = t $