Let X1, ..., Xn be i.i.d. observations. Obtain a UMVUE of a in the following cases.
(a) Xi has the exponential distribution E(a, θ) with a known θ and an unknown a ≤ 0.
(b) Xi has the Pareto distribution Pa(a, θ) with a known θ > 1 and an unknown a ∈ (0, 1].