Suppose that where {t} is a white noise process with finite variance equal to 2.

Zt = 1Zt1 + 2Zt2 + t,

(a) Show that e3 = 1e2 + 2e1 + T +3, where eh = ZT +h zT +h.

(b) Show that CovT (e1,e2) = 12.

(c) Derive an expression for e2(3).