For a linear system with input x(t) and output y(t) find the impulse response for the following cases:
(a) x(t) = e−at u(t), y(t) = u(t) - u( - t)
(b) x(t) = e−t u(t), y(t) = e−2t u(t)
(c) x(t) = δ (t), y(t) = e−at sin btu(t)