(3) Write an expression for the following functions using shifted and scaled versions of the unit step function u(t). (a) 0 -1 3 2 (b) 1 0 -1 (4) Use the sampling property of impulses to compute t38(3t- 6) dt a) b) cos(t) (2t - 4) dt c) t58(3t+ 2) dt (5) Determine if each of the following signals is a power signal, an energy signal, or neither (non- physical). a) x₁(t) = [1 − e−2] u(t) - b) x2(t) = [tcos(3t)] u(t) c) x3(t) = et u(t)