1.17. Determine whether these continuous-time systems are causal or noncausal, have memory or are memoryless. Justify your answers. In the following parts, x() is an arbitrary input and y() is the output response to x(1): (b) y(t) = e(t) (c) y(t) = (sin f)x(1) 1.19. For each of the systems in Problem 1.17, determine whether the system is linear or nonlin- ear. Justify your answers. 1.20. For each of the systems in Problem 1.17, determine whether the system is time invariant or time varying. Justify your answers.