Suppose that Y₁, Y₂,..., Yₙ are a random sample from a population with probability density function
f(y|θ) = { e⁻⁽ʸ⁻θ⁾, 0, y > θ
{ 0 , otherwise,
where θ > 0 is an unknown parameter.
(a) Calculate the method of moments estimator θ₁ of θ.