Let the discrete-time signal be defined by z[n] be defined by (additional values are zero) n a. Express z[n] as a sum of step functions. b. Is z[n] an energy signal, a power signal or neither? If z[n] is an energy signal, compute its energy. If z[n] is a power signal, compute its power. If z[n] is neither, explain why. c. Is z[−n+7] causal? 2. Let the discrete-time signal z[n] be shown below. a. Express z[n] as a sum of step functions u[n]. b. Sketch y[n]=∑m=−11(m+1)z[n−3m]. Remember to label your axes. c. Is z[n] an energy signal, a power signal or neither? If z[n] is an energy signal, compute its energy. If z[n] is a power signal, compute its power. If z[n] is neither, explain why.