O Given these three functions x(t)=2 \delta(t) y(t)=4 u(t) z(t)=e^{-2 t} u(t) x(t) * y(t) \text { where * denotes the convolution integral operation } x(t) * z(t) y(t) *

z(t) y(t) *[y(t)+z(t)]