2.2 For each of the following systems, specify whether or not the system is: (i) linear and/or (ii) time-invariant. (a) y(t) = 3x(t − 1) (b) y(t) = t x(t) (c) dy dt + y(t − 1) = x(t) (d) dy dt + 2y(t) = t −[infinity] x(τ ) dτ (e) y(t) = x(t) u(t) (f) y(t) = [infinity] t x(τ ) dτ (g) y(t) = 2t t x(τ ) dτ