Suppose a physical system is represented by the following system of equations, where u(t) is the input and y(t) is the output: d[ 21 (t) dt [ 22(t) = [ (- 7 2(t = 1) + \u(t)\ ], |u(t)}], y(t)=z1(t+1)+22(t) u(t). 21 (t) For each of the following properties, determine if it applies to the above system and briefly justify your answers (rigorous proofs not needed). Linear Time-invariant Causal Lumped Nonlinear Time-varying Non-causal Distributed Continuous-time Discrete-time