In the circuit of Fig. 1.27, V(1) and Vo(t) are voltages (at time t) and R, and R2 are resistors. There is also an ideal diode that acts as a short circuit when V, is positive and as an open circuit when v, is negative. We view V, and Vo as the system input and output, respectively. (a) Determine an input-output description of this system. (b) Is this system linear? Is it time-varying or time-invariant? Is it causal? Explain your answers. R, Diode i(t) Vo() V,(1) R2