Determine the Laplace transform of the following functions: (a) x_1 (t) = 25 cos(4 pi t 30 degree) delta (t) (b) x_2(t) = 25 cos(4 pi t 30 degree) delta(t - 0.2) (c) x_3(t) = 10 sin(3t)/t u(t) (d) x_4(t) = d^2/dt^2 [e^-4t u(t)]