Obtain and sketch the convolutions of the following signals.

(a) y₁(t) = e^-atu(t) ∗ Il(t - τ), a and τ positive constants

(b) y₂(t) = [II(t/2) + II(t)] ∗ Il(t)

(c) y₃(t) = e^-α|t| ∗ II(t), a > 0 

(d) y₄ (t) = x(t) ∗ u (t), where x(t) is any energy signal [you will have to assume a particular form for x(t) to sketch this one, but obtain the general result before doing so].