5. Compute the Fourier transform of the following signals:
(a) a(t) = (t-4)
(b) b(t) = e^(-2t)(t), where u(t) is the unit step function
c(t) = 3 + sin(2Ï€rt - 4cos(4Ï€rt)
Utilize the results that the Fourier transform of cos(2Ï€fot) is [(f - fo) + (f + fo)] and the Fourier transform of sin(2Ï€fot) is 2i[(f - fo) - (f + fo)].