Determine whether or not each of the following signals is periodic. For periodic signals, determine their periods. a) x1[n] = E-o{8[n 3k] 2 8[n 1- 3k]}. First plot the signal x.[n]. %3D k=-00 b) x2[n] = - x1[-n 1]. First plot the signal x2[n]. c) x,(t) = et sin(2nt) d) x2(t) = Even{sin(4nt) u(t)}. First plot the signal x2(t) %3D