Problem 4. Sketch the following signals: a) b) c) x(t) = u(1) + 5u(1-1)-Zu(1-2) x2(1) = r(t) _ r(t-I)-u(1-2) x a> e) x,(t)=u(cost) Note: ( ) is the unit impulse (see p. 33 of the class notes)