State with reasons whether the following signals are aperiodic or periodic. For periodic signals, find the period and state which of the harmonics are present in the series. a) 3 sin t+2 sin 3t b) 2+5 sin 4t + 4 cos 7t c) 2 sin 3t +7 cos at d) 7 cos nt +5 sin 2nt e) 3 cos (2t)2 + 5 cos 2t f) sin (5t/2) + 3 cos (6t/5)+3 sin((t/7) + (m/12)) g) sin 3t + cos (15t/4) h) (3 sin 2t + sin 5t) i) (5 sin 2t)